Q  D 

30 

S78 

1858 

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// 


••' 


PRINCIPLES  OF  CHEMISTRY. 


THE 


PRINCIPLES   OF  CHEMISTRY, 


ILLUSTRATED    BY 


SIMPLE  EXPERIMENTS. 


DR.  JULIUS  ADOLPII  STOCKHARDT, 

PROFESSOR     IN     THE     ROYAL     ACADEMY     OP     AGRICULTURE    AT    THARAND,      «KD 
^.   INSPECTOR   OF  MEDICINE  IN   8AXON7. 


TRANSLATED    BY 

C.  H.   PEIRCE,   M.   D. 


FOURTEENTH   THOUSAND. 


BOSTON: 
PHILLIPS,  SAMPSON  AND   COMPANY. 

13  WINTER   STREET. 
1858. 


Entered  according  to  Act  of  Congress,  fn  the  year  1851 ,  by 

JOHN    BARTT,KTT, 
la  the  Clerk's  Office  of  the  District  Court  of  the  District  of  MassachusetUr 


PREFACE 


THE  following  work  has  been  translated,  at  the  rec- 
ommendation of  Professor  Horsford,  as  a  good  intro- 
duction to  the  study  of  chemistry. 

Such  alterations  only  have  been  made  in  the  text, 
as  were  required  to  adapt  it  to  use,  in  this  country. 
Other  changes  might  have  been  desirable,  such  as  sub- 
stituting the  hydrogen  for  the  oxygen  scale  of  equiva- 
lent weights,  the  Fahrenheit  instead  of  the  Centigrade 
thermometrical  scale,*  the  adoption  in  every  instance 
of  a  scientific  instead  of  a  popular  nomenclature,  &c. ; 
but,  after  due  deliberation,  it  was  concluded  not  to 
depart  from  the  original,  except  when  absolutely  ne- 
cessary to  do  so.  Where  alterations  in  modes  of  ex- 
pression, &c.,  have  been  made,  the  meaning  of  the 
author  has  been  carefully  retained. 

In.  some  few  instances,  the  scientific  nomenclature 
usually  adopted  in  our  chemical  books  has  been  de- 
parted fro  MI  ;  but  this  could  not  well  be  avoided  with- 
out somewhat  marring  the  character  of  the  original 

*  It  is  highly  probable  that  the  Centigrade  thermometer  will  in  a  few 
years  be  generally  adopted  in  this  country  for  scientific  purposes. 


V)  PREFACE. 

work.  The  changes,  however,  that  have  been  intro- 
duced, will  in  no  way  confuse  the  more  advanced 
student,  even  if  they  do  not  assist  the  learner. 

There  has  been  in  many  cases  great  difficulty  in 
rightly  translating  terms  used  in  the  arts  and  man- 
ufactures, for  the  obvious  reason  that  there  must  be 
many  peculiar  technical  terms  in  use  in  Germany, 
where  arts  and  manufactures,  such  as  porcelain-mak- 
ing, metallurgy,  brewing,  wine-making,  &c.,  are  so 
extensively  cultivated. 

An  important  part  of  the  labor  of  translating  has 
been  performed  by  a  friend,  whose  familiar  knowledge 
of  the  German  language  has  been  to  me  of  much 
value  and  assistance. 

I  am  also  under  great  obligations  to  the  Rev.  Dr. 
Francis,  for  his  kindness  in  looking  over  the  pages 
as  they  issued  from  the  press,  and  for  many  valuable 
suggestions. 

C.  H.  P. 

CaiJibridge,  Sept.  1,  1850. 


NOTE 


THIRD   AMERICAN  EDITION. 


THE  first  American  edition  of  Stockhardt's  "  Princi« 
pies  of  Chemistry,"  translated  from  the  third  German 
edition,  has  been  thoroughly  revised  with  the  fifth,  re- 
cently published,  and  many  alterations  and  additions 
have  been  made;  among  which  are  those  that  refer  to 
Dobereiner's  lamp,  the  section  giving  a  Synopsis  of 
Chemical  Tests,  and  the  Index. 

For  the  sake  of  convenience,  we  have  also  added 
a  table  showing  the  corresponding  degrees  of  the  Cen- 
tigrade and  Fahrenheit's  thermometers;  likewise  a  ta- 
ble of  the  symbols  and  equivalents  of  the  chemical 
elements,  from  the  "Annual  Report  of  the  Progress  of 
Chemistry,  &c.,  No.  V.,  by  Justus  Liebig,  M.  D.,  &c." 
In  this  table  the  equivalent  numbers  are  in  accordance 
with  the  hydrogen  instead  of  the  oxygen  scale,  the  lat- 
ter, having  oxygen  as  100,  being  employed  in  the  body 
of  the  work,  as  in  the  original,  while  the  scale  with 
hydrogen  as  1  is  that  generally  adopted  by  English 
and  American  chemists. 

C.  H.  P. 

Cambridge,  January  1,  1851. 


INTRODUCTION. 


THE  rapid  progress  of  experimental  science  during 
the  last  twenty-five  years  is  to  be  ascribed,  in  great 
measure,  to  the  fact  that  pupils,  as  well  as  instructors, 
have  become  experimenters.  This  is  especially  true 
with  respect  to  chemistry.  For  every  contemporary  of 
Davy,  engaged  in  experimental  researches  in  this  de- 
partment, there  are  probably,  at  present,  scores  of  per- 
sons occupied  in  the  same  field.  The  fruits  of  this  la- 
bor are  to  be  seen  in  the  improved  condition  of  manu- 
factures ;  in  the  more  substantial  scientific  basis  upon 
which  many  processes,  formerly  altogether  empirical, 
are  now  securely  fixed ;  in  the  progress  of  agriculture, 
and  the  arts  generally ;  and,  to  some  extent,  in  the 
progress  of  medicine. 

The  course  of  instruction  to  which  this  greatly  in- 
creased experimental  investigation  is  chiefly  to  be  at- 
tributed, namely,  the  practical  or  experimental  course, 
bears  the  same  relation  to  the  study  of  text-books  on 
chemistry  that  anatomical  dissections  do  to  the  perusal 


X  INTRODUCTION. 

of  essays  on  operative  surgery,  or  the  solutions  of 
problems  in  celestial  mechanics  to  lectures  on  the  ar- 
chitecture of  the  heavens.  It  is,  beyond  question,  the 
most  efficient  method  to  secure  a  sound  and  available 
knowledge  of  the  science,  either  elementary  or  more 
comprehensive. 

Works  designed  to  teach  chemistry  by  experiment 
are  already  in  use,  both  here  and  abroad,  but  most  of 
them  take  for  granted  the  possession  of  expensive  ap- 
paratus, and  a  laboratory;  scarcely  any  are  designed 
to  bring  the  practical  study  of  the  science  within  the 
means  of  the  more  elementary  schools ;  —  and  none 
are  to  be  found  suited  to  the  winter-evening  firesides 
all  over  the  country,  where  the  younger  and  the  more 
advanced  of  both  sexes  would  delight  in  chemical  ex- 
periments, did  not  the .  apparently  necessary  expense  of 
apparatus  forbid  them. 

It  is  to  meet  the  latter  two  wants,  as  well  as  those  of 
a  general  text-book,  that  the  work  of  Professor  Stock- 
fa  ardt,  edited  by  my  late  assistant,  Dr.  Peirce,  is  em- 
inently suited. 

The  apparatus  necessary  for  many  of  the  most  in- 
structive and  interesting  chemical  experiments  would 
cost  but  a  few  dimes,  and  as  many  dollars  would  fur- 
nish the  requisites  for  all,  or  nearly  all,  the  most  impor- 
tant experiments,  if  performed  in  the  simple  manner 
laid  down  in  this  book.  A  few  tubes  and  flasks,  a 
spirit-lamp,  some  corks,  india-rubber  and  reagent  bot- 
tles, almost  complete  the  list.  In  consequence  of  the 


INTRODUCTION.  Xi 

extensive  adoption  of  this  as  an  introductory  work  in 
the  schools  of  Germany,  sets  of  apparatus  to  accom- 
pany it  are  advertised  by  manufacturers. 

The  qualifications  of  this  work,  as  a  text-book  fot 
schools,  are  such  as  to  leave  little,  if  any  thing,  to  be 
desired.  The  classification  is  exceedingly  convenient. 
The  elucidation  of  principles,  and  the  explanation  of 
chemical  phenomena,  are  admirably  clear  and  concise 
The  summary,  or  retrospect,  at  the  close  of  each  chap- 
ter, presenting  at  a  glance  the  essential  parts  of  what 
has  gone  before,  could  scarcely  have  been  more  happily 
conceived  or  expressed  for  the  wants  of  a  pupil  or  an 
instructor. 

The  book  is  also  well  adapted  to  the  wants  of  teach- 
ers who  desire  to  give  occasional  experimental  lectures 
at  a  moderate  expense,  —  and  of  those  who  design  to 
commence  the  study  of  chemistry,  either  with  or  with- 
out the  aid  of  an  instructor. 

E.  N.  HORSFORD, 
Rumford  Professor  in  t/te  University  at  Cambridge 


CONTENTS 


PART    I. 
INORGANIC  CHEMISTRY. 

SECTION 

Chemical  Action, .  .1 

Weighing  and  Measuring, 8 

Specific  Gravity  (Areometer,  &c.),     .                11 

The  Ancient  Division  of  the  Elements, 18 

Water  and  Heat, 21 

Expansion  hy  Heat,  and  Thermometer. 

Expansion  of  Liquids, 22 

Thermometer, 24 

Expansion  of  Solids, 27 

Expansion  hy  Cold, 28 

Melting  of  Solids, 30 

Latent  Heat, 32 

Boiling  and  Evaporation. 

Boiling  of  Water, 34 

Steam, 35 

Aqueous  Vapor,     .                37 

Distillation, 41 

Diffusion  of  Heat. 

Conduction  of  Heat, 12 

Radiation  of  Heat, 43 

Formation  of  Dew, 41 

Solution  and  Crystallization. 

Solution,              ....                 4!> 

Crystallization, .        .  50 

Composition  of  Water,          .                63 

b 


XIV  CONTENTS. 

NON-METALLIC  ELEMENTS.  OR  METALLOIDS. 
first  Group:  Orqanoqens, 

Oxygen  (oxides,  acids,  bases,  salts,  neutralization,  &c.),     ...       56 

Hydrogen  (spongy  platinum,  explosive  gas,  formation  of  water,  chem- 
ical symbols  and  formulas), 8 ' 

Air  (barometer,  safety-tube,  Spritz-bottle,  influence  of  the  air  on  boil- 
ing, current  of  air,  gases,  vapors,  composition  of  air),  ...  91 

Nitrogen  or  Azote, 101 

Carbon  (charcoal,  soot,  coke,  graphite,  diamond,  carbonic  acid,  car- 
bonic oxide  gas),  ....  103 

Combustion  (conditions  of  combustion ;  rapid  and  slow,  complete 
and  incomplete  combustion,  flame,  &c.), Ill 

Retrospect  of  the  Organogens. 

Second  Group :  Pyrogens. 

Brimstone,  Sulphur  (amorphous  and  dimorphous  bodies,  flowers  of 
sulphur,  precipitated  sulphur,  sulphuret  of  iron),    .        .        .        .123 
Sulphuretted  Hydrogen, 132 

Selenium, 137 

Phosphorus, 138 

Phosphuretted  Hydrogen  (predisposing  affinity,  water-bath,  &c.),  .     145 

Retrospect  of  the  Pyrogens. 

Tldrd  Group:  Halogens. 
Chlorine  (nascent  state,  degrees  of  oxidation,  of  sulphuration,  of 

chlorination,  &c.), 150 

Iodine, 155 

Bromine,  Fluorine, 156 

Cyanogen, 157 

Retrospect  of  the  Halogens. 

Fourth  Group:  Hyalogen*. 
Boron  and  Silicon,      .......  .158 

Retrospect  of  the  Metalloids. 

ACIDS. 

first  Group :  Oxygen  Adds. 

Nitric  Acid  (acids,  bases,  neutralization,  &c.),    ...  159 

Nitrous  Acid,  Nitric  Oxide,  Nitrous  Oxide,        .  .261 


CONTENTS.  .    X? 

V 

Carbonic  Acid  (diffusion,  mineral  water,  &c.),  ...  164 

Sulphuric  Acid  (anhydrous,  Nordhausen,  common,  &c.),  .  168 

Sulpnurous  Acid, 174 

Phosphoric  Acid, 176 

Phosphorous  Acid,  Oxide  of  Phosphorus, 177 

Chloric  Acid,  Hypochlorous  Acid,  &c.,  .  .  .  .  .  178 

Cyanic  Acid,  Fulminic  Acid, 179 

Boracid  Acid  (glass,  blow-pipe,  volatilization  of  fixed  substances,  &c.)i  1 80 

Silicic  Acid, 183 

Retrospect  of  the  Oxygen  Acids. 

Second  Group :  Hydrogen  Acids. 

Hydrochloric  Acid  or  Muriatic  Acid  (haloid  salts,  &c.),     .        .        .185 

Aqua  Regia,  or  Nitro-muriatic  Acid, 188 

Ilydrobromic  and  Hydriodic  Acids, 189 

Hydrofluoric  Acid  (etching  on  glass), 190 

Hydrocyanic  or  Prussic  Acid, 191 

Retrospect  of  the  Hydrogen  Acids. 

Retrospect  of  the  Combinations  of  the  Metalloids  with  Oxygen 
and  Hydrogen. 

Third  Group :  Organic  Acids. 

Tartaric  Acid  (tartar,  formation  of  organic  acids,  &c.),      .        .        .194 

Oxalic  Acid, 196 

Acetic  Acid, 198 

Retrospect  of  the  Vegetable  Acids. 

Radicals, 199 

Capacity  of  Neutralization, .        .         200 


LIGHT  METALS. 

First  Group :  Alkali  Metals. 

Potassium  (carbonate  of  potassa,  lye,  nitre,  gunpowder,  chlorate  of 
potassa,  matches,  tartar,  liver  of  sulphur,  &c.),        .        .        .        .20 

Sodium  (common  salt,  Glauber  salts,  carbonate  of  soda,  borax,  solder- 
ing, glass,  &c.), 215 

Ammonia  (dry  distillation,  chloride  of  ammonium,  carbonate  of  am- 
monia, &c.), 227 

Lithium, 23i 

Retrospect  of  the  Alkalies. 


XVJ  CONTENTS. 

Second  Gioup :  Metals  of  the  Alkaline  Earths. 

Calcium  (chalk,  quicklime,  burning  of  lime,  mortar,  gypsum,  cLloride 

of  lime,  &c.), 23^ 

Barium  and  Strontium  (heavy  spar,  &c.), 248 

Magnesium  (Epsom  salt,  white  magnesia,  &c.),          ....    249 
Retrospect  of  the  Alkaline  Earths. 

Third  Group :  Metals  of  the  Earths. 

Aluminum  (clay  and  loam,  Artesian  wells,  arable  soil,  earthen-ware, 
alum,  &c.), 25.°, 

Glucinum,  Yttrium,  Zirconium,  &c.,       ......         26G 

Retrospect  of  the  Earths. 
Retrospect  of  the  Light  Metals. 

Laws  of  Chemical  Combination  (classification  of  chemical  combina- 
tions, chemical  proportions,  equivalents,  atoms,  amorphism,  dimor- 
phism, isomorphism,  atomic  weights), 267 

HEAVY  METALS. 
First  Group  of  the  Heavy  Metals. 

Iron  (oxide  of  iron,  and  ores,  cast-iron,  wrought-iron,  steel,  salts  of 
iron,  green  vitriol,  &c.,  Prussian  blue,  prussiate  of  potassa,  sulphu- 

ret  of  iron,  &c.), 275 

Manganese  (black  oxide  of  manganese,  salts  of  manganese,  &c.),  .  297 

Cobalt  and  Nickel  (smalt,  German  silver,  &c.),          ....  303 

Zinc  (granulated  zinc,  white  vitriol,  distillation  of  zinc,  &c.),         .  309 

Cadmium, 315 

Tin  (tinning,  salts  of  tin,  mosaic  gold,  &c.), 316 

Uranium, 328 

Retrospect  of  the  First  Group  of  Heavy  Metals. 

Second  Group  of  the  Heavy  Metals. 

Lead  (litharge,  sugar  of  lead,  white-lead,  lead-tree,  sulphuret  of  lead, 

&c.), 329 

Bismuth  (fusible  metal,  oxide  of  bismuth,  &c.),    .        .        .  344 
Copper  (oxide  of  copper,  colors  of  copper,  reduction  of  metals,  salts 
of  copper,  blue  vitriol,  verdigris,  sulphuret  of  copper,  alloys  of 

copper,  brass,  &c.), 348 

Mercury  (oxide  of  mercury,  salts  of  mercury,  cinnabar,  amalgams,  &c.),  S  65 

Silver  (alloys,  lunar  caustic,  &c.), 379 

Gold  (alloys,  solution  of  gold,  &c.), 383 


CONTENTS.  XVII 

Platinum  (solution  of  platinum,  spongy  platinum,  &c.),  .         390 

Palladium,  Iridium,  Rhodium,  Osmium,    ...  .  895 

Retrospect  of  the  Second  Group  of  Heavy  Metals. 

TJdrd  Group  of  the  Heavy  Metals. 

Tungsten,  Molybdenum,  Tellurium,  Titanium,  &c.,  .        .                 .    396 
Chromium  (salts  of  chromium,  chrome  yellow,  chromic  acid,  &c.),     397 
Antimony  (tartar  emetic,  Kermes  mineral,  golden  sulphuret,  type- 
metal,  &c.), 402 

Arsenic  (fly-poison,  white  arsenic,   Schweinfurth  green,  orpiment, 

Marsh's  arsenical  test,  &c.), 410 

Retrospect  of  the  Third  Group  of  Heavy  Metals. 

Retrospect  of  all  the  Metals  (metals,  metallic  oxides,  sulphiu  ets, 

chlorides,  oxygen  salts,  occurrence  of  the  metals,  &c.). 
Classification  of  the  more  common  Chemical  Elements. 


PART   11. 

ORGANIC   CHEMISTRY. 

VEGETABLE  MATTER. 

Vegetable  Life  (constituents  of  plants,  organic  radicals,  &c.),      .         .419 
I.    Vegetable   Tissue  (germination,  woody  tissue,  linen,  cotton, 

bleaching,  &c.), 426 

Changes  of  the  Vegetable  Tissue  by  Acids  (gun-cotton,  &c.),  433 
Changes  of  the  Vegetable  Tissue  by  Alkalies,  .  .  .  434 
Changes  of  the  Vegetable  Tissue  by  Heat  with  free  Access 

of  Air, 435 

Changes  of  the  Vegetable  Tissue  by  Heat  without  Access  of 
Air  (charcoal,   illuminating  gas,  wood-vinegar,  creosote, 
wood-spirit,  wood-tar,  pit-coal  tar,  tar- water,  coke,  &e.),     .     436 
Changes  of  the  Vegetable  Tissue  by  Air  and  Water,  or  Pu- 
trefaction and  Decay  (humus,  marsh  gas,  pit-coal,  brown 

coal,  peat,  &c.), 443 

II.  Starch,  or  Fecula  (starch  from  potatoes,  wheat,  and  peas ;  al- 
buminous substances  ;  sago,  inuline,  &c.),      .         .         .         450 
Changes  of  Starch  into  Gum  and  Sugar  (starch-gum,  dex- 
trine, starch-syrup,  malt,  diastase,  mashing,  &c.),        .         .     458 
III.   Gum  and  Vegetable  Mucus  (gum  Arabic,  tragacanth,  cerasine, 

pectine), 464 

C 


XV111  CONTENTS. 

IV.  Sugar  (grape-sugar,  cane-sugar,  liquid  sugar,  sugar  of  milk, 

mannite), 469 

Changes  of  Sugar  by  Heat  and  Acids,      .        .        .        .         47fi 
Retrospect  of  the  Vegetable  Tissue,  Starch,  Gum,  and  Sugar. 
V.  Albuminous  Substances  (albumen,  caseine,  gluten),  .         .     477 

Changes  of  the  Albuminous  Substances  by  Decay  and  Putre- 
faction (formation  of  ammonia  and  nitre),          .  .    479 
Retrospect  of  the  Albuminous  Substances. 
VI.  Conversion  of  Sugar  into  Alcohol  (alcoholic  fermentation),          482 

Wine, 484 

Beer  (surface  fermentation,  bottom  fermentation,  yeast,  &c.),     487 
Brandy  (rectification,  fusel  oil,  &c.),      ....  491 

Spirit  of  Wine,  or  Alcohol  (tinctures,  cordials,  &c.),          .         498 
VII.  Conversion  of  Alcohol  into  Ether  (olefiant  gas,  sulphuric  ether, 

ether,  naphtha,  &c.), 502 

Organic  Radicals  (ethyle), 508 

VIII.  Conversion  of  Alcohol  into  Vinegar  (vinegar  from  brandy,  wine, 
beer,  starch,  and  sugar.    Quick  method  of  making  vinegar. 

Aldehyde,  acetyle,  &c.), 509 

Conversion  of  Sugar  into  Lactic  and  Butyric  Acids  (muci- 
laginous fermentation), 515 

Formation  of  Alcohol,  Acetic  Acid,  and  Lactic  Acid,  on  the 

Baking  of  Bread, 516 

Retrospect  of  the  Changes  of  Sugar  and  Alcohol. 
IX.  Fats  and  Fat  Oils  (oil,  lard,  tallow,  emulsion,  &c.),  .  .  520 
Changes  of  Fat  by  Heat  (olefiant  gas,  illumination,  &c.),  .  528 
Composition  of  Fats  (stenrine,  olcine,  &c.),  ....  532 
Vegetable  Fats  (drying  oils,  unctuous  oils,  &c.),  .  .  534 
Animal  Fats  (tallow,  butter,  fish  oil,  spermaceti,  wax,  &c.),  .  536 
Fats  and  Alkalies,  Soaps  (hard  soap,  soft  soap,  fat  acids, 

oxide  of  glyceryle,  &c.), 540 

Properties  of  Soaps  ;  Insoluble  Soaps  (plaster),        .         .         548 
X.   Volatile  or  Ethereal  Oils  (preparation  of  them,  varieties  of  vol- 
atile oils), 551 

Composition  and  Properties  of  the  Volatile  Oils  (burning 
fluids,  perfumed  distilled  water,  oleo-saccharum,  conversion 

of  the  volatile  oils  into  resin,  &c.), 556 

XI    Resins  and   Gum-Resins  (turpentine  and  balsams,  prepara- 
tion of  the  resins,  kinds  of  resins,  &c.),          .         .         .         568 
Composition  and  Properties  of  the  Resins  (sealing-wax,  lamp- 
black, lac- varnish,  resin  soap,  &c.), 573 

Gum-Resins, ...         582 


CONTENTS.  XIX 

Caoutchouc  (gum  elastic,  gutta  pcrcha),        .        .        .        .58-* 
Retrospect  of  the  F"ats,  Volatile  Oils,  and  Resins. 
XII.  Extractive  Matter  (extracts,  crystallizable  and  uncrystallizable 

extractive  matter,  &c.), 585 

XTII.   Coloring  Matter,  or  Dyes, 590 

XIV.  Organic  Bases  or  Alkaloids-  (morphine,  quinine,  &c.),    .         .  596 
Retrospect  of  the  Extractive  and  Coloring  Substances,  and 

of  the  Vegetable  Bases. 
XV.  Organic  Acids  ^raccmic  acid,  citric  acid,  malic  acid,  tannic 

acid,  &c  ),  .         .     fc. 598 

XVI.  Inorganic  Constituents  of  Plants  (ashes),  arable  soil,    .         .  607 

XVII.  Nourishment  and  Growth  of  Plants,         .                  ...  613 

"  Uncultivated  Plants,  Food  of  Plants,        .        .        .        .  614 

Cultivated  Plants, 615 

Retrospect  of  Vegetable  Matter  in  General. 

ANIMAL  MATTER. 

Animal  Life.     Constituents  of  the  Animal  Body,  &c.,      .        .        .619 

I.  Tlie  Egg  (white  of  eggs,  yolk  of  eggs,  egg-shells),       .        .  622 

II.  The  Milk  (butter,  caseine,  milk-sugar,  &c.),     ....  625 

Digestion, 635 

III.  Tlie  Blood  (fibrine,  blood  corpuscles,  albumen,  &c.),        .        .  636 
Respiration  and  Means  of  Nourishment,      ....  639 

IV.  TJie  Flesh  (juice  of  flesh,  muscular  tissue  boiling  of  meat,  prep- 

aration of  broth  and  soup,  salting  of  meat),         .         .         .  640 

V.  The  Bile, 645 

VI.   Tlie  Skin  ("gelatine,  glue,  leather,  horny  substance.  &c.),  .         .646 

VII.   Tfte  Bones  (bone-earth,  animal  coal,  bone-dust,  &c.),    .         .  654 

VIII     The  So/id  Ern-cinr-nts  ami  i'rine  (urea,  uric  acid,  guano,  Sic.).  .  G.">9 
Retrospect  of  Animal  Matter  in  General. 


A  SYNOPSIS  OF  THE  MOST  IMPORTANT  CHEMICAL  TESTS,"  .       .  C57 

TlIKRMOMETRTCAL  TABLE, 666 

CHEMICAL  SYMBOLS  AND  EQUIVALENTS, 668 

LM>I;X, 663 


PART    FIRST. 
INORGANIC   CHEMISTRY. 

^MINERAL    CHEMISTRY.) 


INORGANIC   CHEMISTRY. 


CHEMICAL    ACTION. 

* 

1.  EVERY  one  knows  that  iron,  heated  to  redness, 
changes  into  scales  or  cinders,  and  that,  exposed  to 
moist  air  or  earth,  it  is  converted  into  rust;  that  the 
expressed  juice  of  the  grape  gradually  turns  to  wine, 
and  this,  again,  to  vinegar ;  that  wood  in  a  stove,  or 
oil  in  a  lamp,  disappears  in  burning ;  and  that  animal 
and  vegetable  substances  in  time  putrefy,  disintegrate, 
and  finally  disappear. 

Iron  cinders  and  rust  are  iron  altered  in  constitution ; 
iron  is  hard,  tenacious,  of  a  grayish-white  color,  and 
brilliant ;  by  heating  to  redness  it  becomes  black,  dull, 
and  brittle ;  on  exposure  to  moisture  it  is  converted  into 
a  powder  of  a  yellowish-brown  color.  Wine  is  altered 
must,  in  which  nothing  of  the  sweet  taste  peculiar  to 
the  grape-juice  can  be  perceived  ;  but  it  has  acquired  a 
spirituous  flavor,  together  with  a  heating  and  intoxicat- 
ing power,  whicji  was  not  in  the  must.  Vinegar  is 
altered  wine ;  it  has  an  acid  smell  and  taste,  and  has 
lost  its  spirituous  flavor,  as  well  as  its  exhilarating 


4:  CHEMICAL    ACTION. 

properties,  its  tendency  being  rather  cooling  and  seda- 
tive. Search  must  be  made  in  the  air  for  the  oil  and 
wood  which  have  disappeared  during  combustion  ;  both 
these  substances  are  converted  into  vapor  or  gas, 
and  warmth  and  light  are  thereupon  evolved  with 
the  phenomenon  of  fire.  Of  a  similar  nature  are  the 
changes  which  animal  and  vegetable  substances  under- 
go, if  kept  for  a  sufficient  length  of  time ;  they  are 
gradually  converted,  as  they  putrefy  or  decay,  into  vari- 
ous kinds  of  gas,  some  of  which  emit  a  very  disagree- 
able odor. 

Such  processes,  by  which  the  weight,  form,  solidity, 
color,  taste,  smell,  and  action  of  the  substances  become 
changed,  so  that  new  bodies  with  quite  different  prop- 
erties are  formed  from  the  old,  are  called  chemical  pro- 
cesses^ or  chemical  action. 

2.  Wherever  we  look  upon  our  earth,  chemical  action 
is  seen  taking  place,  on  the  land,  in  the  air,  or  in  the 
depths  of  the  sea.  The  hard  basalt,  the  glass-like 
lava,  become  gradually  soft,  their  dark  color  passes  into 
lighter,  they  crumble  to  smaller  and  smaller  pieces,  and 
are  finally  changed  to  earth.  A  potato  placed  in  the 
earth  grows  soft,  loses  its  rnealy  taste,  becomes  sweet, 
and  finally  decays.  The  bud,  that  sends  forth  a  sickly 
pale  shoot  in  a  dark  cellar,  when  exposed  to  the  light 
and  air  grows  up  a  vigorous,  firm,  and  green  plant, 
which,  imbibing  its  nourishment  from  the  moist  air  and 
soil,  forms  from  their  elements  new  bodies,  not  to  be 
found  previously  in  the  water  or  the  air.  A  delicate 
network  of  cells  and  tubes  pervades  the  whole  p_ant, 
imparting  to  it  firmness ;  these  we  call  vegetable  tissue, 
or  woody  fibre.  We  find  in  the  saps  which  passes  up 
and  down  through  these  cells,  albumen  and  other  vis- 
cous substances;  in  the  leaves  and  in  the  stalks,  a 


CHEMICAL    ACTION.  O 

green  coloring  matter,  —  chlorophyll;  and  in  the  ripe 
tubers,  a  mealy  substance,  —  starch.  None  of  these  sub- 
stances are  injurious  to  health ;  but  if  the  potatoes 
grow  in  the  dark  and  without  soil,  for  instance,  in  the 
cellar,  there  is  produced  in  their  long  pale  shoots  a 
very  poisonous  body,  solanine. 

The  potato  forms  one  of  our  most  important  articles 
of  food.  The  starch  contained  in  it  is  not  soluble  in 
water,  but  when  received  into  the  stomach  quickly 
undergoes  such  a  change  that  it  can  be  dissolved  or  di- 
gested, and  then  introduced  as  a  liquid  into  the  blood 
The  blood  comes  in  contact  in  the  lungs  with  the  in- 
haled air ;  the  blood  changes  its  color,  the  air  changes 
its  constitution,  and  the  heat  which  we  feel  in  our  bodies 
is  developed.  We  must  conclude,  from  these  changes, 
that  chemical  action  is  going  on  in  our  own  bodies. 

3.  As  long  as  a  plant  or  an  animal  lives,  the  chemical 
processes  are  under  the  guardianship  of  a  higher  mys- 
terious power,  which  is  called  the  vital  force,  and  by 
which  they  are  constrained  to  furnish  the  materials  for 
the  structure  of  the  animal  or  vegetable  bodies.  The 
vital  force  is,  as  it  were,  the  architect  who  plans  the 
building,  and  sees  that  the  requisite  materials  are  pro- 
cured by  the  chemical  processes,  and  worked  up  accord- 
ing to  his  will.  Hereupon  arise  innumerable  new  bod- 
ies, which  cannot  be  artificially  imitated,  as,  for  exam- 
ple, wood,  sugar,  starch,  fat,  gelatine,  flesh,  &c.  They 
are  called  organic  compounds,  or  animal  and  vegetable 
substances,  in  opposition  to  inorganic  or  mineral  bodies, 
which  may  be  artificially  imitated  by  putting  together 
their  constituent  parts.  When  life  in  an  animal  or  veg- 
etable ceases,  the  chemical  powers  obtain  the  mastery, 
and  these,  as  if  they  were  the  grave-diggers  of  nature, 
fulfil  the  old  motto,  —  "Earth  to  earth,  and  dust  to 
1* 


6  CHEMICAL    ACTION. 

dust."  The  leaves  of  the  potato  plant  become  yellow, 
and  then  brown;  they  fall  off,  and  are  gradually  con 
verted  into  a  dark  powdery  substance,  —  humus.  In 
the  course  of  time  even  this  disappears,  with  the  excep- 
tion of  a  little  ashes,  which  cannot  take  flight  with  the 
rest.  What  here  it  takes  years  to  bring  to  pass,  happens 
in  minutes  if  we  throw  the  dry  leaves  into  the  fire.  The 
chemical  action  is  in  both  cases  quite  similar,  —  the  only 
difference  consists  in  the  time  in  which  it  occurs ;  it 
goes  on  rapidly,  as  combustion,  under  a  strong  heat,  and 
slowly,  as  a  process  of  decay,  at  a  moderate  tempera- 
ture. But  what  appears  to  us  annihilation  is  only 
change.  The  substances  which  have  been,  not  an- 
nihilated, but  only  rendered  invisible  by  combustion  or 
decay,  we  find  again  under  another  form,  with  exactly 
the  same  weight,  in  the  air ;  from  the  air,  they  are  again 
'drawn  down  to  the  earth  by  the  chemical  processes 
going  on  in  living  plants. 

4.  We  see  from  this  how  the  inscrutable  power  of 
the  Almighty  appointed  the  chemical  processes  for 
his  servants,  in  order,  by  their  agency,  to  produce  the 
eternal  vicissitude  which  we  daily  observe  around  us  in 
all  nature,  and  to  call  forth  evermore,  in  uninterrupted 
succession,  new  life  from  death  ;  thus  it  is  self-evident 
how  improving  and  instructive  for  every  thinking  man 
must  be  that  science  which  explains  to  him  this  vicissi- 
tude, and  opens  to  him  a  clearer  insight  into  the  won- 
ders of  creation. 

This  deeper  insight  will  not  only  lead  the  mind  of 
mail  to  higher  improvement  and  perfection,  but  must 
also  fill  it  with  greater  admiration  and  profound er  rev- 
erence for  Him,  who  revealed  to  us  in  these  wondeis 
his  unsearchable  omnipotence  and  wisdom. 

In  another  point  of  view,  the  interest  in  chemical 


CHEMICAL    ACTION.  7 

knowledge  will  be  most  powerfully  excited  by  the  use- 
ful application  which  can  be  made  of  it  in  every-day 
life.  Chemistry  teaches  the  apothecary  how  to  com- 
pound and  prepare  his  medicines ;  it  teaches  the  physi- 
cian how  to  cure  maladies  by  means  of  these  medi- 
cines; it  not  only  shows  the  miner  the  metals  con- 
cealed in  rocks,  but  aids  him  also  in  smelting  and 
working  them.  Chemistry,  in  connection  with  physics, 
has  been  the  principal  lever  by  which  so  many  arts 
and  trades  have  been  brought  to  such  a  degree  of  per- 
fection within  the  last  few  decades,  and  by  its  means  we 
have  been  supplied  with  the  numberless  conveniences 
of  life  that  were  not  enjoyed  by  our  fathers.  It  can- 
not be  doubted  that  the  farmer  must  at  once  regard 
chemistry  as  his  indispensable  friend,  for  it  is  this  alone 
which  acquaints  him  with  the  constituent  parts  of  his 
soil,  with  the  proper  nutriment  of  the  plants  he  wishes 
to  cultivate,  and  with  the  means  whereby  he  can  en- 
hance the  fruitfulness  of  his  fields. 

")C5.  Chemical  Force  or  Affinity.  —  If  a  ball  of  iron  be 
heated  to  redness,  till  a  thick  crust  of  scales  is  formed 
around  it,  and  then  weighed,  it  will  be  found  to  have 
increased  in  weight;  consequently,  it  must  have  been 
supplied  with  something  ponderable  from  the  air.  This 
ponderable  substance  is  a  species  of  gas,  called  oxygen , 
by  its  union  with  the  iron  it  has  become  fixed,  yet  by 
other  chemical  processes  it  can  be  reconverted  into  its 
gaseous  form.  If  this  crust  of  iron  is  now  exposed  for 
a  time  to  moisture,  it  will  gradually  become  rust,  and 
again  weigh  more  than  before ;  it  has  attracted  and 
united  to  itself  water,  and  more  oxygen  from  the 
air.  Accordingly,  the  crust  consists  of  iron  and  oxy- 
gen, the  rust,  of  iron,  oxygen,  and  water,  which 
have  become  most  closely  united  with  each  other;  — 


8 


CHEMICAL    ACTION. 


they  are  chemically  combined.  There  is  a  peculial 
power,  which  is  considered  the  cause  of  this  intimate 
union,  as,  in  general,  of  all  chemical  changes ;  it  is  called 
chemical  power  or  affinity,  and  bodies  that  possess  this 
capacity  of  uniting  with  each  other  are  said  to  have  an 
affinity  for  each  other.  Accordingly,  iron  at  a  red  heat 
has  an  affinity  for  the  oxygen  of  the  air,  and  at  an 
ordinary  temperature  it  has  also  an  affinity  for  water. 
A  ducat  changes  neither  its  color  nor  its  weight,  whether 
at  a  glowing  heat,  or  exposed  to  moisture;  we  con- 
clude that  gold  possesses  no  affinity  for  oxygen  or  for 
water. 

6.  A  force  cannot  be  seen  or  grasped;  we  notice  it 
only  in  the  effects  which  it  produces.  If  we  would 
know  whether  a  piece  of  steel  possesses  magnetic 
power,  we  apply  a  needle,  and  try  whether  this  is 
attracted  by  it  or  not;  we  then  conclude  from  its  be- 
haviour as  to  the  absence  or  presence  of  magnetism. 
Precisely  the  same  course,  that  of  experiment,  must  be 
taken,  in  order  to  become  acquainted  with  the  chemi- 
cal forces,  the  affinities  of  bodies  for  each  other.  Every 
experiment  is  a  question  put  to  a  body,  the  answer  to 
which  we  receive  through  a  phenomenon,  that  is, 
through  a  change  which  we  observe,  sometimes  by  the 
sight  or  the  smell,  sometimes  by  the  other  senses.  The 
question  has  just  been  put  to  iron  and  gold,  whether 
they  have  an  affinity  for  oxygen ;  the  iron,  converted  in- 
to black  oxide,  gave  an  answer  to  this  question,  the  un- 
changeable gold  did  not.  Every  change  which  we  per- 
ceive, every  new  property  which  we  observe  in  a  body, 
is  a  letter  in  the  language  of  chemistry.  To  learn  this 
easily  and  thoroughly,  it  is  above  all  things  useful  for  the 
beginner  to  exercise  himself  in  spelling,  that  is,  in  mak- 
ing experiments.  To  give  directions  for  this  is  the  ob 


CHEMICAL    ACTION. 

ject  of  the  present  little  work.  Those  experiments  only 
have  been  introduced,  which,  on  the  one  hand,  can  be 
performed  easily,  safely,  and  without  great  expense, 
and,  on  the  other  hand,  seem  best  adapted  to  illustrate 
the  chemical  doctrines  and  laws,  and  to  imprint  them 
on  the  memory. 

7.  There  are  four  leading  questions  which  the  chem- 
ist puts  to  the  different  natural  bodies. 

a.)  Of  what  are  they  composed?  Take,  for  instance,  a 
piece  of  bone.  How  is  it  affected  when  strongly  heat- 
ed in  a  furnace  ?  It  becomes  whiter,  lighter,  and  less 
solid  than  before  (bone-ashes).  But  how  is  it  affected 
when  heated  in  a  covered  vessel  ?  It  becomes  lighter, 
and  black  (bone-black).  If  exposed  to  boiling  water,  or 
to  steam,  how  is  it  affected  ?  It  becomes  lighter,  and  re- 
mains white ;  but  in  the  water  is  dissolved  glue.  How 
in  muriatic  acid  ?  It  becomes  transparent ;  the  bone- 
earth  is  dissolved,  and  a  gristly  mass  remains,  which, 
when  boiled  with  water,  turns  to  glue.  What  is  the 
action  of  fire  upon  the  glue  ?  In  a  covered  vessel  it  is 
converted  into  coal,  in  an  open  one  it  burns  and  dis- 
appears. These  few  experiments  show  that  the  bone 
contains  a  glue  which  is  combustible,  and  an  earth 
which  is  not  so ;  they  show,  at  the  same  time,  that  it 
is  the  carbonized  glue  which,  in  the  second  experiment, 
colors  the  bone-earth  black,  and  makes  it  bone-black ; 
that  this  glue  is  dissolved  in  water,  but  not  in  muri- 
atic acid,  &c.  Glue  and  bone-earth  are  called  the 
proximate  constituents  of  bone,  but  by  continued  chemi- 
cal processes  these  can  be  resolved  still  further,  that  is, 
separated  into  simpler  constituents.  In  bone-earth  are 
(ound  phosphorus,  a  metal  (calcium),  and  oxygen ,  in 
the  glue,  besides  carbon,  three  other  bodies,  —  oxygen, 
hydrogen,  and  nitrogen,  These  bpdies  can  be  de- 


10  CHEMICAL    ACTION. 

composed  no  further  by  any  known  method  of  analysis 
and  are  therefore  called  simple  bodies,  or  chemical  ele- 
ments. There  are  now  about  sixty  known  elements, 
and  almost  every  year  adds  to  their  number;  but  this  in- 
crease is  of  little  importance  to  chemical  science  or  its 
applications,  for  it  consists  of  elements  which  but  very 
seldom  occur.  This  separating  of  compounded  bodies 
into  simple  ones  is  designated  by  the  name  of  analysis. 

b.)  Wliat  changes  do  bodies  undergo,  when  placed  in 
contact  with  oilier  bodies  ?  Phosphorus,  which  is  ob- 
tained from  bones,  is  luminous  in  the  air,  and  is  grad- 
ually converted  into  an  acid  liquid;  it  unites  with 
the  oxygen  of  the  air,  as  the  iron  did  on  being  heated 
to  redness.  If  the  phosphorus  is  gently  heated,  this 
union  is  attended  with  a  vivid  combustion,  and  there  is 
formed  an  acid  body  which  is  different  from  the  former ; 
to  which,  if  chalk  be  added,  a  new  body  is  formed,  very 
similar  to  bone-ashes ;  it  is  in  fact  artificial  bone-ashes. 
The  number  of  new  bodies  which  may  be  produced  by 
the  union  of  the  elements  with  each  other,  or  with  com- 
pound bodies,  is  infinite,  and  entirely  different  sub- 
stances are  often  formed,  according  as  the  combination 
takes  place  under  the  influence  of  cold  or  heat,  in 
water  or  in  air,  in  greater  or  smaller  quantities.  This 
is  combination  or  synthesis. 

c.)  What  useful  applications  can  be  made  of  chemical 
theory  and  practice?  When  the  chemist  discovers  a 
new  body,  or  a  new  property  in  one  already  known 
or  a  new  method  of  synthesis  or  analysis,  he  imparts 
his  discovery  to  the  apothecary,  the  physician,  the 
farmer,  the  manufacturer,  and  the  tradesman,  that  ex- 
periments may  be  instituted  for  the  purpose  of  ascer- 
taining whether  any  advantage,  facility,  or  improve- 
ment can  be  derived  for  pharmacy,  medicine,  agricul- 


CHEMICAL    ACTION.  11 

ture,  or  the  ,arts.  Phosphorus  ignites  spontaneously 
at  a  gentle  heat ;  it  is  used  in  friction-matches.  Taken 
into  the  stomach  it  acts  as  a  violent  poison ;  it  is  at 
present  the  most  common  means  for  the  extirpation  of 
rats  and  mice.  Bone-ashes  and  gluten  are  the  constitu- 
ents universally  found  in  the  seeds  of  different  kinds  of 
grain ;  the  chemist  concludes  from  this,  that  pulverized 
bones  must  yield  an  excellent  manure  for  grain;  the 
agriculturist  demonstrates  this  by  experiments  on  a 
large  scale.  In  bone-black  the  property  has  been  dis- 
covered of  attracting  many  substances  held  in  solution 
in  liquids,  and  of  condensing  them  in  itself:  on  account 
of  this  property,  it  is  used  for  making  impure  water 
potable ;  the  sugar-refiner  employs  it  to  make  brown 
syrup  colorless ;  with  it  the  distiller  purifies  brandy 
from  fousel  oil.  This  is  applied  or  practical  chemistry, 
d.)  What  are  the  causes  of  chemical  changes,  and 
according  to  what  laws  do  they  take  place?  If  chemical 
experiments  are  performed,  as  they  should  be,  with  the 
balance  in  the  hand,  it  will  soon  be  observed,  that 
when  two  different  bodies  which  can  unite  with  each 
other  are  brought  together,  sometimes  a  part  of  the  one, 
sometimes  a  part  of  the  other,  remains  free.  Further 
experiments  will  show  how  much  of  one  body,  in  weight, 
can  be  united  with  the  other.  If  all  bodies  are  tested 
in  the  same  manner,  the  certainty  is  finally  attained, 
that  all  chemical  combinations  take  place  only  in  fixed, 
unchangeable  proportions,  and  that  to  every  individ- 
ual body  is  assigned  a  definite  weight,  with  which  it 
always  enters  into  any  combination  whatever.  (§  268.) 
This  certainty  is  called  a  natural  law.  Many  such  laws 
of  nature  have  already  been  ascertained,  and  they  serve 
as  a  certain  guide  to  the  chemist  in  his  labors,  since 
they  cannot,  like  human  laws,  be  arbitrarily  evaded  or 


12  WEIGHING    AND    MEASURING. 

changed.  By  them  alone  we  attain  to  a  scientific  in- 
sight into  the  chemical  processes,  and  to  the  capability 
of  putting  direct  questions  to  bodies  by  experiment, 
and  of  testing  the  truth  of  the  answers  received.  An 
explanation  of  the  chemical  processes  based  on  natural 
laws,  which  presents  a  clear  idea  of  the  subject  to  the 
mind,  is  called  a  Tlieory. 


WEIGHING    AND    MEASURING. 

8.  Weighing.  —  The  balance  is  to  the  chemist  what 
the  compass  is  to  the  mariner.  The  ocean  was  indeed 
navigated  before  the  discovery  of  the  compass ;  but  not 
till  after  this  could  the  sailor  steer  with  confidence  to 
a  certain  place,  and  recover  his  proper  course,  however 
often  lost.  And  so,  in  chemistry,  no  systematic  method 
of  study  could  be  pursued  before  the  introduction  of  the 
balance.  The  balance  is  the  standard,  as  well  as  the 
test,  of  chemical  experiments;  it  teaches  us  how  to 
ascertain  the  true  composition  of  bodies,  and  shows  us 
whether  the  questions  put,  the  answers  received,  or  the 
conclusions  drawn  from  them,  are  correct  or  false. 
Hence  it  cannot  be  too  strongly  recommended  to  those 
commencing  the  study  of  chemistry  to  use  the  balance 
even  in  simple  experiments.  For  the  experiments  de- 
scribed in  this  book,  a  common  apothecaries'  balance  is 
all  that  is  requisite. 

Such  a  balance  consists  of  a  brass  beam,  with  arms 
of  equal  length,  through  the  centre  of  which  passes 
a  steel  wedge-shaped  axis,  resting  on  a  hardened 
plate,  so  that  the  beam,  to  the  extremities  of  which  the 
pans  are  attached,  may  easily  vibrate.  It  is  essential 


WEIGHING    AND    MEASURING. 


13 


Fig.  1. 


that  the  axis  should  be  in  the  right  place  of  the  beam, 
a  little  above  its  centre  of  gravity,  as  in  Fig.  1,  a.  The 

centre  of  gravity  can 
be  found  by  balancing 
the  beam  on  its  flat  side, 
with  the  index  attached 
to  it,  on  a  needle,  and 
when  the  beam  rests 
horizontally,  the  point 
of  the  needle  desig- 
nates the  centre  of 
gravity.  If  the  axis  be 
placed  too  low,  beneath 

the  centre  of  gravity,  as  in  Fig.  1,  b,  the  beam  will  over- 
set, if  one  of  the  pans  is  more  heavily  loaded  than  the 
other.  If  placed  directly  in  the  centre  of  gravity,  the 
balance  itself  will  cease  to  vibrate  when  the  beam  is  in 
an  oblique  position.  When  the  axis  is  too  high  above 
the  centre  of  gravity,  the  balance  loses  much  of  its 
sensibility.  This  latter  defect  occurs  most  frequently, 
but  is  easily  remedied  by  lowering  the  axis. 

9.  The  apothecaries'  weight  and  the  French  decimal 
weight  are  those  commonly  used.     The  following   is 
the  table  of  the  apothecaries'  weight,  which  will  an- 
swer for  all  the  experiments  given  in  this  book :  — 

Pound.  Ounces.  Drachms.        Scruples.  Grains. 

1     =    12    =     96    =  288  =  5760 

1    =      8    =    24  =    480 

1    =      3  =      60 

1  =      20 

10.  The  new  French  system  of  weights  and  meas- 
ures^   which   is   now    almost   universally   adopted    by 
chemists,   is  characterized   by  great  simplicity,   all  its 
divisions  being  made  by  ten ;  hence  the  name  decimal 

2 


14 


WEIGHING    AND    MEASURING. 


Fig.  2. 


weight  and  measure.  Its  unit  is  derived  from  the  size 
of  our  globe. 

In  order  to  define  the  different  localities  on  this 
globe,  imaginary  circles,  as  is  well  known,  have  been 
drawn  around  it.  Those  which  pass  round  the  earth 
from  east  to  west,  the  largest  of  which  is  the  equator, 
are  called  parallels  of  latitude  (circles  of  latitude) ; 
ihose  which  pass  round  the  earth  lengthwise,  intersect- 
ing at  the  poles,  meridians  (circles  of  longitude).  The 

parallels  of  latitude  grad- 
ually become  smaller  to- 
wards the  poles  ;  the  me- 
ridians, on  the  contrary, 
are  all  of  equal  size.  The 
circle,  N  E  S  W  N  repre- 
sents a  meridian  or  circle 
of  longitude.  The  fourth 
part  of  this  circle,  or, 
what  is  the  same  thing, 
the  fourth  part  of  the  cir- 
cumference of  our  earth, 

as  N  E,  is  the  basis  of  the  French  system.  This 
quadrant  was  divided  into  ten  million  parts,  one  of 
which  was  taken  as  the  unit,  under  the  name  of  meter. 
A  meter  is  about  three  feet  and  a  quarter  in  length. 
The  smaller  measures  are  produced  by  dividing  by  ten, 
and  are  designated  by  Latin  terms ;  the  larger  ones  by 
multiplying  by  ten,  and  are  designated  by  Greek  terms. 

Smaller  Measures. 

Meter. 

Decimeter    =  T»0  meter. 
Centimeter  =  TJ5     " 
Millimeter  = 


ToSS 


Larger  Measures. 

Meter. 

Decameter   =         10  meters 
Hectometer  =       100      " 
Kilometer    =    1,000      " 
Myriameter  =  10,000      « 


SPECIFIC    GRAVITY.  15 

The  system  of  weights  was  derived  from  the  measure 
of  length,  in'"  the  following  manner.  A  cubical  box 
was  taken,  measuring  exactly  one  centimeter  in  each 
direction,  and  this  was  filled  with  water  at  its  greatest 
density  (at  the  temperature  +4°  C.) ;  the  weight  of 
this  quantity  of  water  was  called  a  gramme*  This  is 
taken  as  the  unit  of  the  decimal  weights,  and  is  multi- 
plied or  divided  by  ten. 

Smaller  Weights.  Larger  Weights. 

Gramme.  Gramme. 

Decigramme  =  ^  gramme.  Decagramme  =  10  gr. 
Centigramme  =  T$5  "  Hectogramme  =  100  " 
Milligramme  =  I0100  "  Kilogramme  =  1,000  " 

Myriagramme  =10,000   " 

One  gramme  is  equal  to  15.44579grs.  Troy. 

One  kilogramme  is  equal  to  21b.  3oz.  4.17dwt.  Av. 

It  is  well  enough  known  that  the  body  wThose  weight 
is  to  be  ascertained  must  be  put  into  one  scale,  and  in 
the  other  weights  sufficient  to  restore  the  index  to  its 
original  perpendicular  position.  The  weight  of  a  body 
thus  determined  is,  in  scientific  language,  called  its  ab- 
solute weight.  Thus,  a  piece  of  sugar  weighing  two 
ounces  has  an  absolute  weight  of  two  ounces ;  or,  if  a 
vessel  be  filled  with  two  pounds  and  one  ounce  of 
water,  this  water  has  an  absolute  weight  of  two  pounds 
and  one  ounce. 


SPECIFIC    GRAVITY. 

11.  ICE  floats  in  water,  iron  sinks  in  it,  because  the 
former  is  lighter,  the  latter  heavier,  than  water.  But  if 
we  put  a  piece  of  ice  in  spirit  it  sinks,  or  if  we  put  a  piece 
of  iron  upon  quicksilver  or  mercury  it  floats;  conse- 
quently, ice  is  heavier  than  spirit,  iron  lighter  than  quick 


16  SPECIFIC    GRAVITY. 

silver.  It  also  follows  that  spirit  is  lighter  than  water 
since  it  can  support  less  weight,  and  quicksilver  heavier 
than  water,  as  it  can  bear  a  greater  weight.  The  terms 
heavier  and  lighter,  in  this  sense,  correspond  to  what  in 
scientific  language  is  called  specifically  heavier  or  specif- 
ically lighter,  and  equal  bulks  are  always  to  be  under- 
stood in  speaking  of  the  comparative  weights  of  bodies. 
The  expression,  ice  is  lighter  than  iron^  means,  therefore, 
that,  taking  equal  bulks  of  each,  the  former  weighs  less 
than  the  latter;  and  when  we  say  that  quicksilver  is 
heavier  thatf  water,  we  mean  that  in  equal  volumes,  as 
a  pint,  for  instance,  the  quicksilver  has  a  greater  weight 
than  the  water.  But  in  absolute  weight,  no  regard  is 
paid  to  the  volume  of  substances. 

In  order  to  ascertain  how  many  times  heavier  quick- 
silver is  than  water,  or  iron  than  ice,  it  is  only  ne- 
cessary to  weigh  equal  volumes  or  portions  of  each, 
and  to  compare  their  weights.  If,  for  example,  we 
take  five  vessels,  each  of  which  would  contain  exactly 
100  grains  of  water,  and  fill  them  respectively  with 
spirit,  ice,  water,  iron,  and  quicksilver,  the  following 
differences  of  weight  will  be  found:  the  vessel  filled 
with  spirit  would  weigh  80  grains ;  with  ice,  90  grains ; 
with  water,  100  grains;  with  iron,  750  grains;  with 
quicksilver,  1,350  grains. 

To  facilitate  the  comparison  of  the  numbers  which 
denote  how  much  greater  the  specific  gravity  of  one 
body  is  than  that  of  another,  water  has  been  fixed  upon 
as  the  standard  or  unit.  Therefore,  in  the  above  case, 
the  question  ib,  How  much  lighter  than  water  are  spirit 
and  ice,  and  how  much  heavier  are  iron  and  quick- 
silver ?  or,  in  other  words,  How  many  times  is  100  con- 
tained in  80,  90,  750,  and  1,350  ?  The  other  numbers, 
then,  are  to  be  divided  by  100,  the  weight  of  water 
and  tbere  is  found  for 


SPECIFIC    GRAVITY.  17 

Spirit,  -f-(^  or,  in  decimals,  0.80 ;  it  is  therefore  -J  lighter 

than  water. "" 
Ice,  -nnr,  or,  in  decimals,  0.90 ;  it  is  therefore  -jV  lighter 

than  water. 
Iron,  -f  JJ,  or,  in  decimals,  7.50 ;  it  is  therefore  7^-  times 

heavier  than  water. 
Quicksilver,  -Sinn  or,  in  decimals,  13.50 ;  it  is  therefore 

13^  times  heavier  than  water. 

These  numbers  represent  the  specific  weights  (sp.  gr.). 
Thus,  according  to  calculation,  spirit  having  a  specific 
gravity  of  0.80,  80  parts  of  it  would  occupy  the  same 
space  as  100  parts  of  water ;  therefore  it  is  only  four  fifths 
as  heavy  as  water,  or,  what  is  the  same  thing,  one 
fifth  lighter  than  water.  The  specific  gravity  of  quick- 
silver being  13.5,  that  is,  13^  parts  of  quicksilver  do 
not  take  up  more  space  than  one  part  of  water ;  since 
it  is  13^-  times  heavier  than  water. 

12.  Determination  of  Specific  Gravity.  —  Experiment. 
—  To  determine  the  specific  gravity  of  a  fluid,  a  vial  is 
weighed,   filled  with  water,  and  then  again  weighed. 
This  gives  the  weight  of  the  water.     Now  pour  out 
the  water,  and  refill  the  vial  either  with  spirit,  syrup; 
lye,  beer,  or  some  other  liquid,  and   ascertain  by  the 
balance  the  weight  of  each.     Then  divide  the  weight  of 
each   of  «these  fluids  by  the  weight  of  the  water,  and 
the  quotient  indicates  the   specific  weight.     It  is  very 
convenient  to  use  a  vial  made  to  contain  exactly  1,000 
grains  of  water,  as  then,  without  any  calculation,  the 
number  of  grains  which  such  a  vial  contains  of  any 
liquid  expresses  its  specific  weight. 

13.  Experiment.  —  Weigh  a  flask  filled  with  water ; 
then   place    a   half-ounce    weight  on    the    pan   which 
holds  the  weights,  and  by  the  side  of  the  flask  nailg 
enough  to  adjust  the  beam.     Remove  both  nails  and 


18 


SPECIFIC    GRAVITY. 


Fig.  3. 


flask  from  the  pan,  and  put  the  nails  into  the  flask.  A 
bulk  of  water  will  be  displaced  equal  to  that  of  the  nails , 
to  determine  its  amount,  replace  the  flask,  after  it  has 
been  thoroughly  wiped  on  the  outside,  upon  the  pan, 
and  remove  weights  from  the  other  pan  until  the  equi- 
poise is  restored.  The  weights  taken  away  (about  32 
grains)  form  the  divisor,  and  the  half-ounce,  or  240 
grains,  the  dividend;  the  quotient  -^3-25-  =  7.5,  is  the 
specific  gravity  of  iron,  of  which  the  nails*  were  made. 
14.  Experiment.  —  If  we  have  to  determine  the 

specific  grav- 
ity of  a  piece 
of  iron,  or  of 
any  other  body 
which  cannot 
be  put  into  a 
flask,  it  must 
be  fastened  by 
a  piece  of  fine 
thread  to  the 
pan  of  a  com* 
mon  balance, 
(Fig.  3,  &,)  the 

cords  of  this  pan  having  been  previously  shortened. 
Weigh  the  body  first  in  air,  and  then  in  water,  immers- 
ing it  an  inch  deep.  As  it  sinks,  the  opposite  pan  falls ; 
consequently  iron  must  be  lighter  in  the  water  than  in 
air.  If  the  iron  in  the  air  weighed  hall  an  ounce,  then, 
in  order  to  restore  the  equilibrium,  it  will  be  necessary, 
as  in  the  former  experiment,  to  remove  from  the  pan  a 
32  grains,  equal  to  the  weight  of  the  bulk  of  water 
displaced  by  the  iron.  The  loss  of  weight  is  the  same, 
whether  the  water  be  removed  from  the  vessel  or  mere- 
V  displaced  within  it.  This  forms  the  divisor,  and  240, 


SPECIFIC    GRAVITY.  19 

the  weight  of  the  iron  in  the  air,  the  dividend,  giving 
the  quotient  \{f L_.  7.5. 

15.  Every  substance  becomes  lighter  in  water  in  pro- 
portion to  the  amount  of  water  displaced ;  this  is  a  law 
of  nature.     If  it  displaces  less  water  than  its  weight  in 
the  air,  it  sinks ;  if  more,  it  floats.     Even   very   heavy 
bodies  can  be  made  to  float  by  increasing  their  volume ; 
ships  are  constructed  of  iron,  although  it  is  eight  times 
heavier  than  water;  a  tumbler  floats  upon  water,  and 
yet  the  specific  gravity   of  glass  is  from  three  to  four 
times  greater  than  that  of  water.     A  thick  piece  of 
iron,  weighing  half  an  ounce,  loses  in  water  nearly  one 
eighth  of  its  weight ;  but  if  it  is  hammered  out  into  a 
plate  or  a  vessel  of  such  a  size  that  it  occupies  eight 
times  as  much  space  as  before,  it  then  loses  its  whole 
weight  in  water,  and  will   float,  sinking  just  to   the 
brirn.     If  made   twice  as    large,  it  will  displace   one 
ounce  of  water,  —  consequently  twice  its  own  weight ; 
it  will  then  sink  to  the  middle,  and  can  be  loaded  with 
half  an  ounce  weight  before  sinking  entirely. 

16.  Areometer,  or  Hydrometer.  —  The  same  body  will 
sink  to  a  greater  or  less  depth  in  different  liquids,  — 
deeper  in  the  lighter  ones,  and  not  so  deep  in  those 
which  are  denser.     This  has  suggested  a  very  conven- 
ient instrument  for  determining  the  spe- 

too  Fl{  cific  gravity  of  liquids,  the  hydrometer 

or  areometer.  This  instrument  consists 
of  a  hollow  glass  tube,  made  as  repre- 
sented in  Fig.  4.  The  interior  is  hol- 
low, and  blown  out  into  a  bulb  at 
the  lower  end,  to  cause  it  to  float ;  the 
under  part  is  loaded  with  quicksilver  or 
shot,  to  give  it  a  vertical  position.  The 
main  tube  serves  to  denote  the  dep^h  to 


20  SPECIFIC    GRAVITY. 

which  it  sinks  in  any  liquid,  by  means  of  a  scale  of 
degrees,  with  which  it  is  furnished.  There  are  vari- 
ous instruments  of  this  kind,  especially  adapted  for 
determining  the  density  of  spirits,  brandy,  oil,  lye,  syrup, 
&c.  If  a  hydrometer  for  weighing  spirits  is  put  into 
water,  it  sinks  only  to  the  lowest  point  on  the  scale  0° 
[Fig.  4,  a)]  but  in  the  strongest  alcohol,  which  is  much 
ighter  than  water,  it  sinks  to  the  highest  point,  100°. 
A  scale  for  testing  lye  (Fig.  4,  b)  must,  on  the  contrary, 
have  the  0°  point  at  the  top  of  the  scale,  to  which  it 
would  sink  in  pure  water ;  for  lye  being  heavier  than 
water,  the  instrument  would  be  more  or  less  buoyed  up 
!n  it,  according  to  its  strength.  In  hydrometers  for 
ighter  liquids,  the  degrees  proceed  from  the  bottom  to 
he  top,  in  those  for  heavier  liquids  from  the  top  down- 
wards. In  most  of  these  scales  the  degrees  are  arbi- 
i^ary  ;  and  in  order  to  convert  them  into  the  correspond- 
i  «g  specific  numbers,  tables,  constructed  for  the  pur- 
p  ^se,  must  be  referred  to. 

17.  Experiment.  —  Pour  brandy  into  a  cylindrical 
ja  ,  and  observe  the  degree  which  it  marks  on  the 
h)  hometer ;  then  put  it  in  a  warm  place,  and,  when 
lul  <*warm,  again  note  the  degree,  which  will  be  higher 
tha  i  before,  as  the  heat  has  expanded  the  liquid,  made 
it  1  ghter,  and  consequently  apparently  stronger  than  it 
realty  is.  (§  22.)  The  specific  gravity  of  all  bodies,  when 
waroied,  is  less  than  when  cold.  On  this  account,  in 
determining  the  density  of  bodies,  regard  should  be 
paid  to  their  temperature,  and  it  has  been  agreed  to 
consider  15°  C.  (§  24)  as  the  mean  temperature. 

In  the  more  accurate  hydrometers,  the  mercury 
serving  as  the  counterpoise  has  been  ingeniously  con- 
trived also  to  indicate  the  degree  of  heat  of  the  liquid 
hv  connecting  with  it  a  graduated  tube.  The  smaJ. 


THE    ANCIENT    ELEMENTS.  21 

Fig  5.  gcalef;:a,  (Fig.  5,)  denotes  the  temperature,  thfl 
long  scale,  b,  the  density.  The  small  scale  is 
frequently  so  constructed,  that  the  degrees  cor- 
respond to  those  on  the  long  scale,  and  in  order 
to  guard  against  error  it  is  only  necessary  to 
add  the  degrees  below  the  mean  temperature 
to  the  density,  or  to  subtract  from  the  density 
those  above. 

Gold  is  nineteen  times,  and  silver  ten  times, 
heavier  than  water;  gold  alloyed  with  silver 
must,  therefore,  have  a  less  specific  weight  than 
pure  gold.  The  specific  weight  of  brass  is 
only  =  8.  Alcohol  and  ether  are  lighter  in  propor- 
tion to  their  purity  and  strength,  while  lye,  syrup,  the 
acids,  &c.,  increase  in  density  according  to  their  purity 
Hence  it  is  evident  how  important  it  is,  in  many  cases, 
to  know  the  specific  gravity  of  a  body  in  order  to 
judge  of  its  quality. 


THE   ANCIENT    DIVISION   OF   THE   ELE 
MENTS. 

18.  Matter  and  Forces.  —  As  we  discern  in  ourselves 
the  visible  body,  and  its  ruler,  the  invisible  spirit,  so 
we  recognize  in   external  nature  bodies  which  we  car 
handle  and  weigh,  and  forces  or  powers  ruling  these 
bodies  and  having  no  weight. 

19.  Aggregation.  —  The  innumerable  natural  bodies 
which  we  meet  with  on  the  earth  may  be  divided  into 
three  great  classes ;  they  are  either  solid)  Aquid,  or  aeri- 
form, and  each  of  these  states  in  which  bodies  exist  is 

called  its  state  of  aggregation. 


22  THE    ANCIENT    ELEMENTS. 

Cohesion.  —  To  divide  a  piece  of  ice  into  smaliei 
fragments,  a  greater  force  is  requisite  than  to  separate 
water  into  minute  portions ;  whence  we  infer  that  the 
particles  of  the  solid  ice  adhere  more  strongly  than 
those  of  the  fluid  water.  A  certain  attracting  power  is 
regaided  as  the  cause  of  this  difference ;  it  acts  on  the 
very  smallest  particles  of  matter,  and  is  called  cohesion 
or  homogeneous  attraction.  In  solid  bodies,  cohesion 
is  stronger  than  in  liquids,  and  in  aeriform  bodies  hard- 
ly a  trace  of  it  can  be  perceived. 

The  Ancient  Elements,  so  called.  —  Of  solid  bodies,  the 
most  widely  diffused  is  earth ;  of  liquids,  water ;  and  of 
the  aeriform  bodies,  air.  From  this  the  ancient  phi- 
losophers concluded  that  all  solid  matter  was  formed 
of  earth,  all  liquids  of  water,  and  aeriform  bodies  of 
air ;  on  this  account  they  called  them  elements,  or  pri- 
mary matter.  They  cannot  now  be  regarded  as  such  in 
a  chemical  point  of  view,  since  they  have  been  decom- 
posed into  still  more  simple  bodies ;  but  they  may  be 
viewed  as  physical  elements,  that  is,  as  types  of  the 
three  aggregate  states  of  bodies. 

20.  We  have  no  absolute  knowledge  of  the  forces  of 
nature,  they  having  as  it  were  a  spiritual  existence.  We 
are  nevertheless  as  firmly  convinced  of  their  reality  as 
we  are  of  the  reality  of  our  own  spirit,  for  we  know  them 
by  their  phenomena  and  effects.  A  piece  of  iron,  on 
being  thrown  into  the  air,  falls  to  the  ground,  which  is 
ascribed  to  the  power  of  gravitation ;  if  exposed  to  a 
moist  atmosphere,  it  rusts,  that  is,  it  unites  with  the 
oxygen  of  the  air.  This  is  the  result  of  chemical  force ; 
and  the  force  of  electricity  can  free  the  iron  again 
from  this  union.  By  the  force  of  magnetism,  a  piece 
of  iron,  when  balanced  on  a  pivot,  takes  a  direction 
from  north  to  south;  by  the  force  of  heat  it  can  be 


WATER    AND    HEAT.  23 

melted,  &c.,  &c.  From  this  it  appears  that  there  are 
various  forces,'but  it  is  not  improbable  that  they  have 
one  common  origin,  in  the  same  way  that  all  the  differ- 
ent powers  of  the  mind,  will,  imagination,  judgment, 
&c.,  are  all  referred  to  one  single  spirit. 

Fire,  the  fourth  of  the  old  elements,  may  be  regarded 
as  the  symbol  of  these  forces.  This  also  has  lost  its 
place  among  the  chemical  elements,  since  it  is  merely 
a  phenomenon  of  chemical  processes  affording  light 
and  heat. 

Of  these  old  elements,  fire  (heat),  water,  and  air 
play  an  important  part  in  most  chemical  experiments ; 
heat  being  influential  in  promoting  chemical  changes, 
and  water  being  the.  most  usual  solvent  of  solid  and 
aeriform  bodies.  The  air  deserves  consideration  in  all 
cases,  for  almost  all  chemical  experiments  are  per- 
formed in  it,  and  it  may  exert  injurious  or  beneficial 
effects  upon  them.  These  three  so-called  chemical  ele- 
ments will  therefore  first  be  more  particularly  con- 
sidered. 


WATER    AND    HEAT. 

21.  WATER  covers  about  three  quarters  of  the  sur- 
face of  the  globe;  it  exists  sometimes  solid,  as  at 
the  poles,  and  sometimes  fluid,  as  in  warmer  regions. 
In  the  form  of  rivers  it  intersects  the  land  in  all 
directions;  while  it  rises  in  vapor  into  the  air,  and, 
forming  clouds,  returns  in  rain  to  the  earth.  Thus  we 
find  it  in  nature  in  its  three  aggregate  forms,  and  it  is 
obvious  that  these  external  differences  have  been  effect- 
ed by  the  agency  of  heat.  Hence  water  is  peculiarly 


24  WATER  AND  HEAT. 

well  adapted  to  serve  as  a  study  of  the  most  impor- 
tant effects  of  heat. 


EXPANSION  BY  HEAT,  AND  THERMOMETER. 

22.  Expansion  of  Liquids.  —  Experiment.  —  Take  the 
tare  of  a  flask,  —  that  is,  place  it  on  one  of  the  pans 
of  a  balance  and  equipoise  it  by  weights  put  into  the 
opposite  pan ;  —  then  fill  it  with  water,  and  ascertain  the 
weight  of  the  latter.     Warm  the  flask  on  a  tripod  over 
a  simple  spirit-lamp,  moving  it  round 
gently  at  first,  that  the   flask  may 
heat  gradually.     The  water  will  soon 
rise,  and  part  of  it  run  over.     When 
it  begins  to  boil,  remove  the  lamp 
and   let    the   vessel    cool,   and  the 
water  will  then  sink  deeper  than  it 
stood  before.     How  much  has  been 
displaced   is  found   by  its   loss    in 
weight ;  it  will  amount  to  about  -}-% 
of  the  first  weight. 

The  burning  spirit,  or  alcohol,  heats  the  bottom  of 
the  glass  vessel,  which-  in  turn  communicates  heat  to 
the  water.  The  heat  expands  the  water,  consequently 
it  occupies  a  greater  space  than  before,  and  part  of  it 
must  run  over.  Hence  it  follows  that  warm  water 
must  be  lighter  than  cold  water.  If  a  pitcher  filled  with 
two  pounds  of  ice-cold  water  be  afterwards  filled  with 
boiling  water,  it  will  weigh  about  an  ounce  and  a  half 
less.  As  it  cools,  it  contracts  again  to  its  former 
density. 

The  same  occurs  with  all  other  liquids,  and  indeed 
also  with  solids  and  gases :  hence,  it  may  be  stated  as 
a  natural  law,  that  all  bodies  expand  by  heat,  and  con- 


EXPANSION  BY  HEAT,  AND  THERMOMETER.     25 

tract  on  cooling.  But  the  amount  of  expansion  is  very 
different  in  different  bodies  at  the  same  temperature; 
alcohol,  for  example,  expands  two  and  a  half  times 
more,  mercury  two  and  a  half  times  less,  than  water. 
When  fluids  are  to  be  bought  and  sold  by  measure,  an 
advantageous  application  may  be  made  of  this  prin- 
ciple. If  a  hundred  measures  of  brandy  or  alcohol  are 
purchased  in  hot,  and  sold  in  cold  weather,  there  will 
be  a  loss  of  four  or  five  measures ;  therefore  we  should 
gain  by  buying  in  winter  and  selling  in  summer. 

23.  Experiment.  —  In  order  to  observe  more  accurate- 

ly  the  expansion  of  water  by  heat,  adapt  to 
a  flask  a  cork,  rendered  so  soft  by  gentle 
pounding  that  it  may  be  exactly  fitted  to 
the  opening  by  mere  pressure ;  perforate 
the  cork  with  a  round  file,  and  make  the 
hole  just  large  enough  to  admit  a  glass 
tube.  Fill  the  flask  with  water,  so  that, 
when  the  cork  is  firmly  pushed  in,  the 
water  shall  stand  at  about  a,  (Fig.  7,)  and 
heat  it  as  in  the  former  experiment. 

The  water,  which  in  the  former  experi- 
ment was  displaced  from  the  flask,  in  this 
case  rises  in  the  tube,  and  the  higher  in  proportion  to 
the  smallness  of  its  bore.  By  this  means  very  slight 
changes  of  space  are  rendered  visible,  and  these  de- 
viations may  be  applied  to  the  measurement  of  heat. 
This  is  done  by  particular  instruments  called  ther- 
mometers. 

24.  Thermometer.  —  Water  might  be  employed  for 
measuring  heat,  by  marking  the  boiling  and  freezing 
points,   and   graduating   the    intervening    space ;    but 
mercury  is  far   better   adapted   to  the  purpose,   as  it 
boils  and  freezes  at  greater  extremes  of  temperature, 

3 


26  WATER    AND    HEAT. 

and  more  rapidly  denotes  the  variations  of  heat  and 
cold. 

The  vessel  containing  the  mercury  may  also  be 
regarded  as  consisting  of  a  flask  and  tube,  but  which, 
instead  of  being  joined  by  a  cork,  are  composed  of  one 
entire  piece.  Having  introduced  into  it  a  sufficient 
quantity  of  mercury,  and  sealed  the  open  end  by 
fusion,  it  is  immersed  in  melting  snow,  and  the  point 
to  which  the  quicksilver  falls  is  marked  freezing-  point ; 
that  to  which  it  rises  in  boiling  water,  boiling  point. 
The  space  between  these  two  points  can  now  be  divid- 
ed into  degrees,  to  form  the  scale.  The  degrees  below 
the  freezing  point  are  of  the  same  dimensions  as  those 
above.  There  are  several  scales  in  use.  though  it  is  to 
be  regretted  that  more  than  one  has  been  adopftd.  The 
most  common  are  the  three  following:  —  Reaumer^s 
(R.),  divided  into  eighty  degrees;  the  centigrade  of 
Celsius  (C.),  into  one  hundred  ;  and  Fahrenheit's  (F.), 
into  one  hundred  and  eighty  degrees.  The  difference 
between  these  can  be  easily  seen  in  the  annexed  figure 
According  to  R.  water  freezes  at  0°  and  boils  at  80° ; 
according  to  C.  it  freezes  at  0°,  and  boils  at  100° ;  ac- 
cording to  F.  it  freezes  at 
+32°,  and  boils  at  2123. 

Fahrenheit,  a  philosophical- 
instrument  maker,  commenced 
counting,  very  strangely,  not  at 
the  freezing  point,  but  at  32° 
below  it.  His  scale  is  still  in 
common  use  in  England,  and 
the  high  numbers  found  in 
English  reckonings  are  thus 
accounted  for.  In  Germany 
Rcawmer's  thermometer  is  used. 


EXPANSION  BY  HEAT,  AND  THERMOMETER.     27 

except  "for  scientific  purposes,  when  the  Centigrade,  in 
common  use  in  France,  is  employed,  and  it  has  been 
adopted  in  this  work.  In  order  to  compare  these  ther- 
mometers with  each  other,  it  need  only  be  remembered 
that  4°  R.  are  as  large  as  5°  C.  or  9°  F.  In  reduc- 
ing Fahrenheit  to  Reaumer  or  Centigrade,  if  the  de- 
gree be  above  the  freezing  point,  32°  must  first  be  sub- 
tracted, which  process  must  be  reversed  in  order  to  re- 
duce the  degrees  of  the  other  scales  to  those  of  Fahren- 
heit. To  the  degrees  above  0°,  the  sign  -f-  is  prefixed, 
to  those  below,  the  sign  — . 

A  cylindrical  thermometer,  graduated  to  300°  C., 
Fig.  9.  like  that  in  the  annexed  figure,  is  best  suited  for 
chemical  experiments,  as  it  can  be  easily  adapted 
to  a  perforated  cork,  and  then  fitted  to  a  flask,  in 
which  liquids  are  to  be  heated  to  a  certain  tem- 
perature. The  degrees  above  the  boiling  point 
are  to  be  divided  off  at  distances  equal  to  those 
below. 

25.  Quicksilver  freezes  at  —40°  C.  In  the 
northern  regions  of  the  earth  a  degree  of  cold 
of  — 50°  C.  has  been  observed,  and  by  artificial 
means  the  temperature  can  be  lowered  to  — 10CP  C. 
When  great  degrees  of  cold  are  to  be  measured,  alco- 
hol is  used  in  the  construction  of  this  instrument,  as 
it  does  not  congeal  at  — 1003  C. 

26.  Quicksilver  boils  at  360°  C.,  therefore  its  use 
must  be  limited  to  temperatures  below  this  point. 
The  high  temperatures  attending  ignition  are  measured 
by  the  expansion  of  platinum  bars,  a  metal  which  does 
not  melt  even  in  the  hottest  farnace.  Such  an  instru- 
ment is  called  a  pyrometer.  By  means  of  lenses,  and 
by  chemical  action,  a  degree  of  heat  of  more  than 
2000°  C.  may  be  produced, 


28 


WATER    AND    HEAT. 


27.  Expansion  of  Solids.  —  If  an  iron  vessel,  when 
cold,  is  just  large  enough  to  pass  through  the  door  of  an 
oven,  it  cannot  be  removed  from  it  when  heated.  The 
iron  bands  or  tires  of  carriage  wheels  are  applied  while 
red-hot  to  the  frame,  and  on  cooling  they  contract  and 
bind  the  wood-work  together  with  great  force.  A  metal- 
lic disk,  which,  when  red-hot,  fits  exactly  into  a  circular 
box,  will,  on  cooling,  become  loose,  and  shake  in  it. 
The  tire  and  the  disk  both  become  smaller  on  cool- 
ing. These  examples  show  that  solids  also  are  ex- 
panded by  heat,  and  contracted  by  cold,  and  explain 
many  of  the  phenomena  of  common  life.  Clocks  go 
faster  in  winter,  and  slower  in  summer,  because  the 
pendulums  elongate  in  summer,  and  consequently  vi- 
brate slower,  while  in  winter  they  become  shorter,  and 
vibrate  more  rapidly.  A  piano  gives  a  higher  tone  in 
a  cold  than  in  a  warm  room,  on  account  of  the  contrac- 
tion of  the  strings;  a  nail  driven  into  the  wall  becomes 
loose  after  a  time,  because  the  iron  expands  in  summer 
and  contracts  in  winter  more  than  the  stone  or  the 
wood,  and  thus  the  opening  is  gradually  enlarged. 
For  this  reason,  in  the  construction  of  railroads  the 
rails  must  not  be  laid  too  close  together;  in  the  ar- 
rangement of  steam-pipes,  these  must  not  be  too  firmly 
inclosed ;  in  roofing,  the  zinc  plates,  instead  of  being 
nailed  together,  must  overlap  each  other,  that  they  may 
neither  tear  nor  warp  on  alternate  contraction  and  ex- 
pansion. 

Brittle  bodies,  as  glass  and  porcelain,  expand  or  con- 
tract so  rapidly,  by  sudden  heating  or  cooling,  that  they 
break, 

Experiment.  — Wind  round  a  vial  two  bands  of  paper 
a  and  6,  Fig.  10,  and  secure  them  firmly  with  thread 
a  cord   round   the   vial,   between  these  folds  of 


EXPANSION  BY  HEAT,  AND  THERMOMETER.     29 

FV  iOj-  paper,  and  move  the  vial  quickly 

to  and  fro  on  the  cord  until  the 
latter  breaks.  Then  immediately 
pour  cold -water  upon  the  place, 
and  the  glass  will  break  as  even- 
ly as  if  cut.  The  sharp  edges  can 
be  removed  with  a  file.  In  this 
manner,  common  vials,  and  Cologne,  and  even  larger, 
bottles,  may  be  converted  into  vessels  adapted  to  chem- 
ical and  other  purposes. 

It  is  well  known  that  heat  is  produced  by  the  friction 
of  two  bodies  upon  each  other ;  that  by  sliding  quickly 
down  a  line  or  a  pole  by  the  hands,  these  will  be  burnt, 
and  that  rapid  motion  will  ignite  the  axles  of  a  carriage, 
unless  they  are  well  greased.  Thus,  in  the  above  ex- 
periment, the  friction  produced  great  heat  in  the  glass, 
the  string  emitted  a  burnt  odor  and  broke,  and  great 
expansion  of  the  glass  was  produced.  When  the 
outer  surface  was  suddenly  cooled  by  the  cold  water, 
the  expanded  particles  at  once  contracted,  and  more 
rapidly  in  the  external  particles  than  in  those  of  the 
inner  surface,  causing  the  fracture  of  the  glass;  and  the 
more  easily  the  greater  its  thickness.  If  the  tempera- 
ture had  been  slowly  reduced,  it  would  not  have 
broken. 

Thus,  it  is  obvious,  (a,)  that  glass  and  porcelain  ves- 
sels intended  for  sustaining  high  temperatures,  such 
as  flasks,  alembics,  retorts,  capsules,  &c.,  should  be  thin, 
particularly  at  the  bottom ;  and  (b)  that,  when  used, 
they  should  always  be  gradually  heated  and  cooled. 

The  above  method  of  heating  glass  by  a  cord  fur- 
nishes the  apothecary  with  a  simple  expedient  for  re- 
mo  \ng  stoppers  which  are  too  firmly  fixed  in  the  bot 
tie?    to    be   taken   out   by    turning   or   tapping   them 
3* 


30 


WATER    AND    HEAT. 


Fig.  11. 


Wind  a  cord  round  the  neck  of  the  bottle,  and  move  it 
quickly  until  sufficient  heat  has  been  produced  to  loos- 
en the  stopper. 

No  two  solids  expand  alike ;  the  metals  expand  the 
most,  and  all  solids  less  than  fluids. 

The  expansion  of  gaseous  bodies  will  be  c:.  nsidercd 
under  the  head  of  air.  (§  97.) 

28.  Expansion  by  Cold.  —  A  remarkable  exception  to 
this  law,  of  expansion  by  heat,  and  contraction  by  cold, 
occurs  in  the  case  of  water. 

Experiment.  —  A  large  flask  is  arranged  as  directed 
in  experiment  23,  inserting  also  a 
cylindrical  thermometer,  #,  through 
a  hole  made  in  the  cork.  The  flask 
is  filled  with  water  to  the  top  of  the 
tube  fr,  and  placed  in  a  vessel  filled 
with  snow.  A  strip  of  paper  may  be 
pasted  on  this  tube,  upon  which  the 
level  of  the  water  may  be  marked  as 
the  thermometer  falls.  The  water  as 
it  cools  will  sink  in  tjie  tube  until 
the  mercury  stands  at  4°  C. ;  yet  on 
cooling  still  more  it  does  not  fall  any 
farther,  as  we  should  expect  it  would 
but,  on  the  contrary,  it  begins  to  rise 
again,  and  continues  to  do  so  till  it  reaches  the  freezing 
point.  At  0°  C.  it  stands  at  the  same  point  as  when 
its  temperature  was  at  8°  C.  Water  is  accordingly 
the  densest  at  -j-4°  C. ;  all  other  liquids  continue  tc 
increase  in  density  as  they  cool. 

29.  However  unimportant  this  exception  may  appeal 
at  first,  our  admiration  must  be  the  greater  when  we 
reflect  upon   its  consequences.     Were  it  not  for  this, 
our   counfry   would   have   the   climate  of    Greenland, 


MKLTIXG    OF    SOLIDS.  3t 

The  freezing  of  our  waters,  as  the  winter  sets  in,  is 
principally  owing- to  the  coldness  of  the  atmosphere. 
Consequently,  the  upper  part  of  the  water  is  colder  and 
heavier,  and  sinks  to  the  bottom ;  the  warmer  watei 
ascends,  becomes  cold,  and  also  sinks.  If  the  water 
continually  became  denser,  to  its  freezing  point,  this 
circulation  would  continue  till  the  whole  mass  of  water 
to  its  greatest  depth  reached  0°  C.,  and  a  few  cold 
days  would  suffice  to  convert  all  our  ponds,  lakes,  and 
rivers  into  ice.  This  does  not  happen,  because  the  cir- 
culation ceases  when  its  temperature  has  fallen  to  4° 
C. ;  when  the  water,  though  yet  colder,  becomes  light- 
er, and  floats  on  the  surface.  Thus,  freezing  can  only 
take  place  at  the  surface,  and  the  ice  be  but  gradually 
formed.  At  a  small  depth  below  the  ice,  the  water 
always  retains  the  temperature  of  4°  C. 

MELTING  OF  SOLIDS. 

30.  The  expansion  of  bodies  is  the  first  general 
effect  of  heat;  but  in  solid  bodies  another  effect  is  ob- 
served; they  change  their  aggregate  state,  they  be- 
come liquid,  they  melt.  Many  of  them  become  soft  be- 
fore melting,  so  that  they  can  be  kneaded ;  for  instance, 
butter,  glass,  and  iron ;  in  this  condition,  glass  can  be 
bent  and  moulded  like  wax,  and  iron  can  be  forged. 

Experiment.  —  Hold  a  piece  of  a  small  glass  tube  in 
the  upper  part  of  the  flame  of  a  spirit-lamp,  revolving 
it  slowly  between  the  fingers  ;  \vhen  red-hot,  it  will  be 
so  soft  that  it  can  be  bent  into  any  shape  desired. 
Thus  are  easily  formed  any  of  the  numerous  bent  tubes 
required  in  chemical  experiments.  For  softening  larger 
tubes,  a  lamp  with  a  double  blast  must  be  used,  as  this 
gives  a  much  stronger  heat  than  the  simple  lamp.  Tc» 


32  WATER    AND    HEAT. 

break  a  glass  tube,  a  scratch  is  made  upon  it  with  a 
three-cornered  file,  at  the  place  to  be  broken,  and  then 
it  can  be  parted  by  gently  pulling  with  both  hands. 

Most  solid  bodies  become  suddenly  fluid,  as  ice,  lead, 
&c. 

31.  Experiment.  —  Place  one  vessel  containing  snow 
or  ice,  and  another  containing  a  piece  of  tallow,  on  a 
warm  stove,  testing  from  time  to  time  the  melthig  sub- 
stances with  a  thermometer ;  the  temperature  »vill  re- 
main stationary  in  the  first  vessel  at  0°  C,  in  the  other  at 
about  38°  C.,  so  long  as  any  ice  or  tallow  remains  un- 
melted,  but  when  the  melting  is  complete  it  will  com- 
mence rising.    The  degree  of  heat  at  which  a  body  melts 
is  called  its  melting'  point.    Every  substance  has  its  own 
melting  point,  sometimes  above  and  sometimes  below 
the  freezing  point;   for  example,  lead  melts  at  above 
300°  C.,  silver  at  above  1000°  C.;  solid  quicksilver  at 
— 40°  C.     If  these  two  vessels   containing  water  and 
melted  tallow  are  placed  in  the  cold,  it  will  be  observed 
that  the  tallow  soon   hardens   at  about  -j-35°  C.,  but 
the  water  not  until  the   mercury  has  fallen  to  0°  C. 
Thus  the  congelation  of  fluids  takes  place  at  about  that 
temperature  at  which  they  pass  from  the  solid  to  the 
fluid  state. 

Many  substances,  coal  for  instance,  have  never  yet 
been  melted,  and  others  have  never  been  frozen,  as, 
for  instance,  alcohol ;  but  it  is  very  probable  that,  when 
some  method  of  producing  the  greatest  degrees  of  cold 
and  heat  is  discovered,  we  shall  succeed  in  rendering  all 
solid  bodies  liquid,  and  all  liquids  solid. 

32.  Latent   Heat.  —  Experiment.  —  Put   two   vessels 
of  equal  size  on  the  hearth   of  a  warm  oven,  one   of 
them  containing  a  pound  of  snow  at  0°,  and  the  other 
a  pound  of  water  at  0°  ;  when  the  snow  is  melted,  re- 


MELTING    OF    SOLIDS.  3 

move  them  both.  By  the  touch  merely  it  will  be  per- 
ceived that  the  snow-water  is  still  cold,  while  the  water 
in  the  other  vessel  has  become  warm ;  and  the  thermom- 
eter will  indicate  that  in  the  former  the  temperature 
is  at  0°  C.,  in  the  latter  at  75°  C.  Both  vessels  have 
received  equal  degrees  of  heat,  and  when  put  into  the 
oven  were  of  the  same  temperature;  the  question  then 
suggests  itself,  What  has  become  of  the  75°  of  heat 
imparted  to  the  vessel  filled  with  snow?  The  reply  is, 
This  heat  has  been  absorbed  by  the  snow,  thus  convert- 
ing it  into  a  fluid,  —  melting  it. 

Experiment.  —  Put  one  pound  of  snow  at  0°  C.  into 
the  vessel  containing  the  water  heated  at  75°  C.,  and 
then  test  with  the  thermometer ;  as  soon  as  all  the  snow 
has  disappeared,  the  quicksilver  will  fall  to  the  freezing 
point.  Consequently  the  snow  has  taken  from  the  hot 
water  75°  C.  of  heat,  and  has  thus  become  liquid. 

33.  Experiment.  —  This  heat  has  by  no  means  been 
annihilated  in  the  water,  but  is  concealed  there  (latent), 
and  continues  thus  hidden  as  long  as  the  water  exists  in 
a  fluid  state.  But  it  will  again  become  free,  or  sensible 
to  the  touch,  when  the  water  assumes  a  solid  form.  This 
may  be  rendered  obvious  by  sprinkling  £  of  an  ounce 
of  water  upon  1^  ounce  of  quicklime  ;  the  lime  swells, 
becomes  very  hot,  and  finally  crumbles  into  a  fine 
powder.  If  this  is  weighed  when  cold,  it  will  be  found 
to  have  increased  in  weight  by  half  an  ounce;  thus 
two  ounces  of  slaked  lime  have  been  produced  from 
an  ounce  and  a  half  of  quick  lime ;  the  quarter  of  an 
ounce  of  water  missing  has  passed  off  as  steam.  The 
water  alone  could  have  effected  this  increase  ol  weight 
by  combining  chemically  with  the  lime;  and  it  can 
exist  there  only  in  a  solid  state,  as  the  slaked  lime  is  an 
entirely  dry  pulverulent  substance.  This  great  devel- 


34  WATER    AND    HEAT. 

opment  of  heat  can  be  explained  thus :  partly  because 
the  water,  in  becoming  solid,  gives  up  the  heat  which 
it  had  absorbed  in  passing  to  the  fluid  state,  and  partly 
because  of  the  chemical  combination  between  the  two 
bodies  taking  place  with  great  energy.  A  disappear- 
ance of  heat  always  ensues  when  solid  bodies  become 
fluid;  but  an  evolution  of  heat,  on  the  contrary,  when 
liquid  bodies  become  solid;  and  thus  is  explained  very 
simply,  for  example,  why  the  air  remains  cool  when 
the  snow  and  ice  are  melting  in  the  spring,  and  why 
the  weather  moderates  on  the  fall  of  snow. 

That  heat  which  is  felt  by  us,  and  which  is  indicat- 
ed by  the  thermometer,  is  called  free  heat;  it  has  but  a 
feeble  affinity  for  bodies,  and  easily  leaves  them  on 
cooling.  That  imperceptible  heat  on  which  the  fluidity 
of  liquid  bodies  depends,  and  which  on  freezing  escapes 
or  becomes  free,  is  called  latent  heat.  Hence  a  fluid 
may  be  regarded  as  a  combination  of  a  solid  with  la- 
tent heat. 


BOILING  AND  EVAPORATION. 

34.  Boiling  of  Water.  —  Water,  as  is  well  known, 
boils  when  heated  to  a  certain  temperature. 

p.    12  Experiment.  —  Water,  to  which 

some  sawdust  has  been  added,  is 
heated  in  a  test-tube  over  a  spirit- 
lamp.  The  tube  is  held  by  the 
upper  part,  and  rotated  for  some 
minutes  between  the  fingers,  that 
the  flame  may  have  equal  access 
to  all  the  lower  parts  of  the  tube. 
If  the  water  be  carefully  observed, 
it  will  be  seen  that  the  sawdust  ascends  on  the  upper 


BOILING    AND    EVAPORATION. 


Fig.  13. 


surface  of  the  liquid,  and  descends  in  the  lower  strata ; 
the  warm  water,  becoming  lighter,  rises  upwards,  while 
the  colder,  consequently  heavier,  water  sinks ;  the  water 
circulates.  In  consequence  of  this  circulation,  the  heat- 
ing of  fluids  takes  place  more  rapidly  when  the  heat  is 

applied  beneath.  Test-tubes 
are  cylindrical  glass  vessels 
with  rounded  bottoms.  To 
prevent  their  breaking  on  the 
application  of  heat,  the  bot- 
tom must  be  thin,  and  blown 
of  a  uniform  shape.  A  sim- 
ple wooden  rack,  as  in  the 
serves  as  a  convenient  stand  for 


annexed 
them. 


figure, 


Experiment.  —  Repeat  the  former  experi- 
ment, using  instead  of  the  tube  a  flask, 
and  omit  the  sawdust,  so  that  the  water 
may  remain  clear;  in  a  short  time  many 
little  bubbles  will  appear  on  the  walls  of 
the  flask,  which  will  gradually  increase  in 
size,  and  rise  towards  the  surface.  These 
bubbles  consist  of  air,  which  is  expanded 
by  heat  and  expelled  from  the  water.  All 
spring-water  contains  some  air  in  solution, 
and  to  this  is  chiefly  due  its  refreshing 
taste,  which  is  not  found  in  boiled  water  or 
in  that  which  has  been  standing  for  some 
time.  Afterwards,  when  the  water  has  be- 
come quite  hot,  larger  bubbles  appear  on 
the  hotter  part  of  the  flask,  which,  also  ascending,  be- 
come smaller  and  entirely  disappear  before  reaching  the 
surface  of  the  water ;  they  consist  of  aeriform  water 
(steam),  which  condenses  as  it  comes  in  contact  with 


36  WATER    AND    HEAT. 

the  cooler  liquid  above.  The  collapsing  of  the  particles 
of  water  a.-  the  places  where  these  steam-bubbles  dis- 
appear occasions  that  peculiar  noise  which  precedes 
boiling,  and  which  is  commonly  called  the  singing  of 
the  water.  When  the  whole  mass  of  water  is  heated  to 
100°  C.,  these  bubbles  no  longer  condense,  but  rise  to 
the  surface,  where,  surrounded  by  a  thin  film  of  water, 
they  remain  quiescent  for  a  few  seconds,  and  then,  their 
watery  mantle  again  sinking,. they  finally  burst.  This 
is  the  boiling'  of  water.  It  boils  at  100°  C. ;  other 
liquids  boil  more  readily,  —  alcohol,  foi*  instance,  at 
80°  C. ;  others  again  more  difficultly,  —  mercury,  for  in- 
stance, at  360°  C. 

35.  Steam.  —  The  space  above  the  boiling  water  in 
the  interior  of  the  flask  appears  vacant,  but  it  is  in  fact 
filled  with  aeriform  water,  which  has  displaced  the  air 
that  was  in  it.  This  aeriform  water  is  called  steam. 
It  is  almost  1700  times  lighter  than  water,  because 
a  measure  of  water  yields  nearly  1700  measures  of 
steam  at  100°  C.  "Within  the  flask  the  steam  is  trans- 
parent and  invisible,  but  in  the  open  air  it  ascends 
in  the  form  of  white  clouds,  which  greatly  increase  if 
cold  air  is  blown  into  the  flask  by  means  of  a  glass 
tube.  On  cooling,  the  transparency  of  the  vapor  is" dis- 
turbed, on  account  of  the  formation  of  drops  of  water, 
so  small  and  light  as  to  float  in  the  air.  Clouds  also 
consist  of  this  partly  condensed  vapor.  As  the  con- 
densation increases,  the  drops  become  so  large  and 
heavy,  that  they  descend'  as  rain.  A  thermometer  im- 
mersed in  boiling  water  indicates  100°  C. ;  if  placed  in 
the  steam  immediately  above,  it  shows  the  same ;  and 
this  temperature  will  not  rise  higher,  however  long  the 
boiling  be  continued,  or  however  strongly  the  flame  of 
the  lamp  be  urged.  This  is  similar  to  what  occurs  in 


BOILING    AND    EVAPORATION. 

the  melting  of  snow ;  heat  disappears,  and  its  disap- 
pearance proceeds  from  the  same  cause  in  both  cases; 
steam  requires  heat  for  its  existence  as  such,  and  is  so 
intimately  combined  with  it  that  the  excess  is  no  longer 
perceptible,  —  it  is  latent.  If  water  may  be  regarded 
as  a  combination  of  ice  with  latent  heat,  so  steam  may 
be  considered  as  a  combination  of  ice  with  still  more 
latent  heat;  which  latter  becomes  free  again  on  the 
conversion  of  steam  into  water. 

36.  Experiment.  —  Adapt  the  shorter  limb  of  a  bent 
glass  tube,  by  means  of  a  perforated  cork,  to  the  neck 
of  a  flask,  and  pass  the  longer  limb  to  the  bottom  of  a 
beaker-glass  or  common  tumbler.     Pour  into   each  ot 
Fig.  15.  these  two  vessels 

two  ounces  and 
a  half  of  ice-cold 
water,  and  grad- 
ually heat  the 
glass  upon  a  tri- 
pod until  it  boils. 
Note  the  time  re- 
quired for  this 
operation.  Con- 
tinue the  process 
until  the  water  in 
the  beaker-glass  begins  to  bubble,  and  note  also  the 
time,  which  will  be  found  the  same  as  that  required  for 
heating  the  water  in  the  flask.  The  steam  formed  in 
the  flask  has  no  other  outlet  than  through  the  tube  into 
the  water,  where  it  condenses,  until  the  contents  of  the 
second  glass  reach  the  temperature  of  100°  C.,  and 
boil. 

Both  of  the  vessels  must  now  be  weighed;  and  it 
will  be  found  that  the  flask  weighs  half  an  ounce  less 
4 


38  WATER    AND    HEAT. 

and  the  beaker-glass  half  an  ounce  more  than  before, 
consequently,  half  an  ounce  has  passed  from  the  for- 
mer as  steam,  and  has  been  condensed  again  in  the 
latter;  and  yet  this  half-ounce  of  steam,  which  it- 
self was  not  hotter  than  100°  C.,  could  heat  to  the 
boiling  point  two  ounces  and  a  half  of  ice-cold  water. 
What  is  the  source  of  these  500  additional  degrees  of 
heat?  They  were  latent  in  the  steam,  and,  on  its 
being  condensed,  were  set  free.  These  were  caused  by 
the  heat  of  the  spirit-lamp,  as  must  be  obvious  from 
the  above-noted  amount  of  time  consumed.  Assuming 
that  the  time  required  to  boil  the  water  in  the  first  flask 
was  ten  minutes,  and  also  ten  minutes  for  boiling  the 
water  in  the  second  vessel,  it  follows,  that  the  same 
amount  of  heat  which  was  required  for  heating  two 
ounces  and  a  half  of  water  was  only  sufficient  to  evap- 
orate half  an  ounce  of  water ;  the  whole  heat  given  out 
in  the  last  ten  minutes  from  the  spirit-lamp  must  con- 
sequently have  been  converted  into  latent  heat.  If  half 
an  ounce  of  boiling  water  received  during  the  evapora- 
tion the  amount  of  500°  of  heat,  then  the  steam 
evolved  must  have  given  off  just  as  much  heat  when  it 
again  assumed  a  liquid  state ;  consequently,  it  must  be 
able  to  raise  the  temperature  of  two  ounces  and  a  half 
of  water  at  0°  C.  to  that  of  100°  C. 

The  property  of  steam  to  absorb  a  large  quantity  of 
heat,  and  to  part  with  it  again  during  condensation, 
peculiarly  adapts  it  for  the  heating  of  other  bodies,  the 
burning  of  them  being  thus  guarded  against,  as  the 
heat  of  steam  in  open  vessels  can  never  exceed  100°  C. 
Apothecaries  avail  themselves  of  steam  in  the  prepara- 
tion of  infusions,  decoctions,  and  extracts ;  it  serves  for 
many  of  the  processes  of  cookery,  and  for  the  distilla- 
tion of  spirits ;  it  is  employed  in  dyeing  and  bleaching 


BOILING    AND    EVAPORATION.  39 

establishments,   and  is   often  resorted   to  for  heating 
apartments,  buildings,  laundries,  &c. 


AERIFOBM. 


SOLID. 


The  increase  and  decrease  of  heat  produced  by 
change  of  the  aggregate  state  of  bodies  will  be  made 
clear  by  the  annexed  diagram.  As  the  steam  ascends 
in  the  direction  of  the  arrows  (by  liquefaction  and 
evaporation)  heat  becomes  latent,  and  as  it  descends 
(condensation  of  vapor  and  congelation  of  fluids)  heat 
is  liberated. 

37.  Aqueous  Vapor.  —  Water  exposed  in  a  vessel  to 
the  open  air  disappears  in  summer  more  rapidly  than  in 
winter;  the  heat  of  the  air  renders  it  aeriform, — it  evap- 
orates. The  same  happens  as  in  evaporation  over  the 
fire,  only  in  the  former  case  evaporation  takes  place 
without  any  visible  motion  of  the  water,  owing  to  its 
becoming  aeriform,  not  throughout  the  whole  mass  at 
once,  but  upon  the  surface  only.  Vapor  rises  in  an  in- 
visible form  in  the  air.  Warm  air,  indeed,  receives 
more  of  it  than  cold,  but  a  fixed  quantity  of  it  only  for 
each  temperature.  Thus  one  hundred  measures  of  air 
at  0°  C.  absorb  two  thirds  of  a  measure  of  vapor ;  at 
10°  C.,  one  measure  and  a  quarter;  at  20°  C.,  two  and 
an  eighth  measures,  &c.  If  the  air  has  not  yet  absorbed 
all  the  vapor  which  it  can,  it  eagerly  takes  up  more,  as, 
for  example,  when  one  hundred  measures  of  air  at  20°  C 


40  WATER    AND    HEAT. 

contain  only  one  or  one  and  a  half  measures  of  vapor 
it  is  then  called  dry  air,  and  wet  articles  are  soon  dried 
in  it  by  rapid  evaporation.  But  if  it  be  already  saturat- 
ed with  vapor  it  is  called  moist  air ;  and  damp  articles 
cannot  be  dried  in  it,  or  at  least  but  slowly.  If  yet  more 
vapor  be  added  to  this  saturated  atmosphere,  or  if  it  be 
cooled,  then  the  excess  separates  in  visible  particles, 
called  mist  or  fog  when  they  lie  upon  the  surface  of 
the  earth,  and  clouds  when  they  float  in  the  higher 
regions  of  the  atmosphere.  The  white  smoke  which  in 
winter  is  seen  rising  from  the  chimneys,  the  visibleness 
of  the  breath  in  frosty  weather,  and  the  smoking  of 
rivers  in  winter  and  after  a  storm,  are  phenomena  of 
the  same  kind. 

38.  If  the  cooling  of  the  air  is  occasioned  by  a  cold 
solid  body,  the  vapor  is  then  condensed  in  small  drops 
of  water,  as  may  be  observed  on  the  outside  of  a  cold 
glass  when  brought  into  a  warm  room,  and  the  deposit 
of  moisture  on  the  inside  of  our  window-panes,  when 
cooled  by  the  external  cold  air.  The  temperature  at 
which  this  occurs  is  called  the  dew-point,  signifying  the 
temperature  at  which  the  air  is  saturated  with  vapor. 
Experiment.  —  Fill  a  tumbler  one  quarter  full  with 
cool  water,  place  in  it  a  thermometer,  and 
at  short  intervals  gradually  add  ice  or  cold 
water,  until  moisture  begins  to  deposit  on 
the  outside  of  the  glass.  Then  observe 
the  degree  indicated  by  the  thermometer 
which  is  the  dew-point.  If  much  cold 
water  must  be  added  before  the  glass 
clouds  over,  that  is,  if  the  dew-point  is  much  lower 
than  the  temperature  of  the  air,  fair  weather  ma)  be 
expected ;  while,  on  the  contrary,  if  the  difference  be- 
tween the  dew-point  and  the  temperature  of  the  air  be 


BOILING    AND    EVAPORATION.  41 

but  slight,  rain  ,may  soon  be  expected,  as  then  the  air 
requires  but  a  slight  addition  of  moisture  or  increase  of 
cold  to  become  saturated.  Instruments  by  means  of 
which  the  amount  of  moisture  in  the  air  is  ascertained 
are  called  hygrometers.  Many  substances  readily  im- 
bibe moisture  from  the  air,  and  become  damp;  such 
bodies,  for  instance,  as  catgut,  carbonate  of  potassa,  sul- 
phuric acid,  fresh  barley-sugar,  &c.,  are  called  hygro- 
scopic. 

39.  Evaporation  may  be  accelerated,  not  only  by  heat, 
but  also  by  a  current  of  air,  because  by  this  means 
the  air  above  the  surface  of  the  fluid,  which  is  charged 
with  vapor,  is  removed  and  replaced  by  a  drier,  and,  as 
it  were,  more  thirsty  air,  which  takes  up  the  vapor  more 
rapidly  and  abundantly  than  the  former.     For  this  rea- 
son, the  earth  dries  rapidly  after  rain,  when  followed 
by  a  high  wind,  and  hence   it  is  necessary   in   kilns, 
laundries,  drying-rooms,  &c.,  to  arrange  them  in  such  a 
manner  that   the   air,  when  saturated   with  moisture, 
may  be  constantly  replaced  by  dry  air. 

40.  That  heat  disappears  during  slow  as  well  as  rapid 
evaporation  (§  36)  may  be  readily  illustrated  by  the  fol- 
lowing experiment. 

Experiment.  —  Fill  a  tube  half  full  of  water,  and 
fasten  securely  round  the  bulb  of  it  a  piece 
of  cloth ;  saturate  the  cloth  with  cold  water, 
and  then  twirl  the  tube  rapidly  between  the 
hands ;  presently  the  water  in  the  tube  will 
become  sensibly  colder,  and  the  degree  of 
cold  may  be  accurately  determined  by  the 
thermometer.  Moisten  the  cloth  with  ether, 
a  very  volatile  liquid,  and  twirl  it  again  in  the 
same  manner  as  before ;  by  which  means  its 
contents,  even  in  summer,  may  be  convert- 
4* 


42  WATER    AND    HEAT. 

ed  into  ice.  Water  evaporates  slowly,  ether  rapid- 
ly ;  and  both  require  heat  for  their  conversion  into 
vapor,  and  in  the  above  experiment  they  obtain  this 
heat  from  the  water  in  the  bulb,  which  is  of  course  the 
reason  of  the  water  becoming  cold.  On  this  principle, 
one  feels  cool  on  just  leaving  the  bath,  when  invested 
in  damp  garments,  or  when  the  floor  of  a  hot  apart- 
ment is  sprinkled  with  water.  It  explains,  also,  how 
man  is  enabled  to  support  the  scorching  sun  of  the 
hottest  climates,  and  even  to  endure  a  heat  of  100°  C., 
without  his  blood  exceeding  the  temperature  of  from 
38°  to  40°  C. ;  it  is  owing  to  the  more  copious  per- 
spiration, which,  by  evaporation,  renders  all  the  heat 
above  40°  C.  latent.  If  we  blow  on  hot  soup,  it  is  also 
the  increased  evaporation  which  cools  it  more  rapidly ; 
but  if  we  blow  on  the  cold  hands  in  winter,  they  be- 
come moist  and  warm,  because  the  latent  heat  con- 
tained in  the  vapor  of  the  breath  is  set  free,  as  the 
vapor  is  condensed  into  water. 

41.  Distillation.  —  If  evaporation  be  carried  on  in  a 
rlose  vessel,  the  water  may  be  collected  as  it  forms. 

Experiment.  —  A  small  glass  retort  is  half  filled  with 

water,  and  heat- 

r  ig.  IB. 

ed ;  the  steam,  as 
it  forms,  passes 
through  the  neck 
of  the  retort  in- 
to a  glass  receiv- 
er, contained  in  a 
vessel  filled  with 
cold  water,  and 
»s  there  condensed.  That  the  refrigeration  may  take 
place  more  rapidly,  the  receiver  is  covered  with  coarse 
blotting-paper,  which  is  frequently  moistened  by  cold 


DIFFUSION    OF    HEAT.  43 

water.  This  .operation  is  called  distillation  (from  dis- 
tillare^  to  drop),  aricl  the  pure  water  obtained  is  said  to 
be  distilled.  It  is  purer  than  spring-water,  for  this  rea- 
son, that  the  non-volatile,  earthy,  and  saline  portions 
contained  in  all  spring-water  do  not  ascend  with  the 
vapor,  but  remain  in  the  retort.  By  this  means  very 
volatile  bodies  also  can  easily  be  separated  from  less 
volatile  ones ;  as  brandy  from  the  less  volatile  water. 
Copper  stills  are  usually  employed  for  distillation  on  a 
large  scale,  and  for  condensers  vats  are  constructed 
holding  serpentine  pipes,  or  worms,  which  present  a 
greater  condensing  surface  than  if  the  pipe  had  passed 
directly  through  the  vat.  The  cold  water  with  which 
the  vats  must  be  filled  is  very  soon  warmed  by  the  heat 
liberated  in  the  condensation  of  the  steam,  and  must 
occasionally  be  renewed  by  leading  off  the  hot  water 
from  above,  and  letting  in  a  fresh  supply  of  cold  water 
beneath. 


DIFFUSION  OF  HEAT. 

42.  Conduction  of  Heat.  —  Experiment. —  A  test-tube, 
nearly  filled  with  water,  is  held 

Fig.  19.  ••1.1 

over  a  spint-lamp,  in  such  a 
manner  as  to  direct  the  flame 
against  the  upper  layers  of  the 
water ;  the  water  will  boil  at  the 
top,  but  remain  cool  below.  If 
mercury  is  treated  in  a  similar 

way,  its  lower  layers  will  gradually  become  heated. 
The  particles  of  mercury  will  communicate  the  heat  to 
each  other,  but  not  so  the  particles  of  water.  Sub- 
stances through  which,  as  in  mercury,  heat  rapidly 
passes,  are  called  conductors  ;  but  bodies  which  comport 


44  WATER    AND    HEAT. 

like  water  are  called  non-conductors  of  heat.  In  the 
former  class  are  included  particularly  the  metals,  and  in 
the  latter,  stone,  glass,  wood,  snow,  water,  and  especial- 
ly cloth,  fur,  linen,  straw,  paper,  ashes,  &c. 

The  conductors  are  readily  heated,  and  soon  become 
cold  again,  as  is  well  known  to  be  the  case  with  iron 
stoves.  A  piece  of  iron  feels  hotter  in  the  sun  and 
colder  in  the  shade  than  a  piece  of  wood  at  the  same 
temperature.  The  explanation  of  this  delusion  of  the 
sense  of  touch  is,  that  the  warm  iron  conducts  the  heat 
more  rapidly  to  the  hand,  while  the  cold  iron  withdraws 
it  more  rapidly  than  the  wood  is  capable  of  doing. 

The  non-conductors  of  heat  are  slowly  heated,  and 
also  slowly  cooled ;  for  this  reason,  stoves  constructed 
of  brick  (the  Russian  stove)  and  those  made  of  Dutch 
tiles,  a  preparation  of  clay,  retain  their  heat  longer  than 
iron  stoves.  Non-conductors  are  frequently  employed 
both  for  preventing  the  quick  heating  and  the  quick 
cooling  of  bodies.  Vessels  of  glass  and  porcelain  are 
placed  on  sand  (a  sand-bath)  or  ashes,  to  heat  them 
gradually,  and  thus  guard  against  their  breaking.  If  a 
hot  liquid  is  to  be  poured  into  them,  it  must  be  done  by 
small  portions  at  a  time,  twirling  the  vessels  round  for 
some  minutes  before  adding  more. 

On  removing  a  vessel  from  the  fire,  the  precaution 
should  be  taken  never  to  place  it  while  hot  on  metal  or 
stone,  but  always  on  some  non-conductor,  such  as 
straw  (straw  rings),  wood,  paper,  cloth,  &c. ;  as  they  are 
often  cracked  by  sadden  cooling  and  contraction,  which 
is  also  frequently  caused  by  a  current  of  cold  air. 
Doors  of  furnaces,  ladles,  &c.,  are  provided  with  wooden 
handles  to  prevent  those  using  them  from  being  burnt. 
Should  a  person  desire  to  hold  a  flask  or  a  test-tube 
while  liquids  are  boiling  in  them,  he  must  wrap  round 


DIFFUSION    OF    HEAT.  45 

them  several  folds  ^of  paper,  or  tie  round  them  a  piece 
of  twine,  in  order  that  they  may  serve  as  a  non-con- 
ductor between  the  glass  and  his  fingers.  By  inclos- 
ing substances  in  non-conductors,  the  entrance  of  cold, 
or,  more  correctly,  the  departure  of  heat,  may  be  pre- 
vented ;  this  principle  is  illustrated  in  our  method  of 
clothing,  in  the  protection  given  to  our  wells  and  trees 
by  covering  them  with  straw,  in  the  preservation  of  the 
seeds  of  plants  by  snow,  and  in  numerous  other  phe- 
nomena of  daily  occurrence.  Hence  non-conductors  are 
frecruently  called  preservers  of  heat. 

43.  Radiation  of  Heat.  —  By  conduction,  bodies  can 
communicate  or  abstract  heat  only  when  in  contact. 
But  heat  is  felt  even  at  some  distance  from  a  fire  or 
from  a  heated  stove,  and  the  earth  is  warmed  by  the 
sun,  although  a  space  of  millions  of  miles  is  between 
them.  This  sort  of  heating  is  called  radiation  of  heat. 

Experiment.  —  Envelop  three  tumblers  with  paper, 
one  with  silver  paper,  another  with  white,  and  a  third 
with  dull  black  paper,  and  place  them  in  the  sun ;  a 
thermometer  will  indicate  that  the  tumbler  with  the 
black  paper  is  heated  the  most,  and  that  with  the  silver 
paper  the  least,  and  yet  all  these  vessels  have  been 
equally  exposed  to  the  rays  of  the  sun.  This  differ- 
ence is  explained  on  the  principle,  that  the  sun's  rays 
are  reflected  from  light-colored  and  shining  bodies, 
whilst  they  are  absorbed  by  those  which  have  a  dull, 
dark  color.  From  this  absorption  it  would  seem  that 
the  light  of  the  sun's  rays  is  converted  into  heat.  It 
explains  why  black  clothes  keep  us  warmer  than  white 
ones ;  why  the  snow  melts  more  rapidly  when  soot  or 
dark  earth  is  scattered  upon  it;  and  why  grapes  and 
other  fruits  ripen  quicker  against  dark  walls  than 
against  those  having  a  light  color. 


46  WATER    AND    HEAT. 

If  hot  water  is  poured  into  the  tumblers  enveloped 
with  paper,  and  the  cooling  of  it  noted  by  the  ther- 
mometer, the  contrary  effect  will  be  observed;  the  glass 
covered  with  black  paper  will  first  become  cold,  and  that 
wrapped  in  silver  paper  the  last ;  because  bodies  with 
dull  surfaces  radiate  the  heat  more  rapidly  than  those 
with  polished  surfaces.  For  this  reason,  coffee  retains 
heat  longer  in  a  bright  than  in  a  tarnished  pot ;  a  stove 
of  glazed  Dutch  tiles  remains  hot  longer  than  another 
of  unglazed  tiles ;  a  smooth  sheet-iron  stove,  longer 
than  a  similar  one  of  rough  cast-iron,  &c. 

The  radiation  of  heat  enables  us  to  explain  some  of 
those  common  natural  phenomena  which  otherwise 
would  remain  obscure.  Why  do  not  the  rays  of  the 
sun,  even  in  the  hottest  summers,  melt  the  snow  upon 
the  tops  of  high  mountains,  which  are  nearer  than  the 
level  portions  of  the  earth  to  the  sun  ?  Because  they 
only  heat  those  bodies  which  can  absorb  their  warmth, 
as  the  rough  surface  of  the  earth.  The  snow  is  indeed 
struck  by  the  rays  of  the  sun,  but  being  a  white  and 
shining  body  it  reflects  them  and  remains  cold. 

44.  Formation  of  Dew.  —  When  the  surface  of  the 
earth  has  become  warm,  the  air  is  heated  by  it ;  hence, 
during  the  day  the  lower  strata  will  always  be  warmer 
than  the  upper.  But  a  change  takes  place  after  the 
sun  has  gone  down.  The  earth  continues  to  radiate 
heat  without  receiving  any  in  exchange,  and  its  tem- 
perature consequently  diminishes.  Neither  does  the  air 
so  readily  part  with  its  heat,  and  therefore  it  attains  dur- 
ing the  night  a  higher  temperature  than  the  surface  of 
the  earth  ;  it  is  only  cooled  where  it  comes  in  contact 
with  the  colder  earth.  If  this  cooling  should  reach  the 
dew-point  of  the  air  (§38),  then  the  vapors  are  con- 
densed, on  the  soil  or  on  vegetation,  in  the  form  of 


SOLUTION    AND    CRYSTALLIZATION. 


47 


small  drops,  just  as  a  tumbler  is  covered  with  vapor 
when  brought  from  a  cold  into  a  warm  room,  —  dew 
iorms.  If  the  temperature  of  the  earth  sinks  in  the 
night  to  the  freezing  point,  or  below  it,  the  aqueous 
vapor  is  deposited  in  a  solid  form,  and  is  called  frost. 

The  radiation  of  heat  from  the  earth  is  greatest  when 
the  weather  is  clear  and  serene ;  but  it  is  obstructed  by 
clouds  and  wind.  Thus  the  most  copioul  deposit  ol 
dew  takes  place  only  in  clear  and  quiet  nights.  The 
clouds  serve  as  a  screen  in  reflecting  back  to  the  earth 
the  rays  of  heat,  so  that  it  can  only  cool  gradually. 
The  same  effect  is  produced  by  the  mats,  straw,  and 
boards  with  which  the  gardener  covers  his  young 
plants  to  protect  them  from  the  late  frosts  of  spring,  or 
from  freezing.  The  annexed  figure,  in  which  arrows 
denote  the  direction  of  heat,  will  serve  to  render  this 
process  more  intelligible. 


Sunbeams. 


Fig.  20. 


Surface  of 
the  earth. 


150 


In  the  day-time 


50 
Dew. 


(P 

Frost. 


In  clear  and  serene  nights. 


120 

No  dew  or  frost. 


Cloudy  or  windy 
nights. 


50 
No  dew  or  frost. 


Cle-ir  ni?hts. 
Soil  protected. 


SOLUTION   AND  CRYSTALLIZATION. 

45.   Solution.  —  Water  can  dissolve  many  bodies,  and 
unite  intimately  with  them,  without  losing  its  transpai- 


48  WATER  AND  HEAT. 

ency.  Such  combinations  are  called  solutions.  If  rain- 
water meets  with  soluble  substances,  either  in  the  earth 
or  in  the  rocks  through  which  it  oozes,  it  dissolves 
them ;  and  this  explains  why  almost  all  spring-water, 
as  it  evaporates,  yields  an  earthy  or  saline  residue. 
Frequently  this  residue,  particularly  when  it  contains 
lime,  is  so  altered  during  evaporation,  that  it  can  no 
longer  be  dissolved  in  water,  and  forms  a  hard  in- 
crustation round  the  inner  sides  of  the  vessels  used  in 
cookery.  The  springs  of  Carlsbad  deposit  so  much 
residue,  that  articles  immersed  in  them  appear  in  a 
short  time  to  be  externally  petrified  or  incrusted.  If 
water  is  unusually  rich  in  soluble  substances,  especially 
such  as  possess  medicinal  properties,  as,  for  example, 
iron,  sulphur,  &c.,  it  receives  the  name  of  mineral  water, 
and  the  springs  from  which  it  issues  are  called  mineral 
springs.  A  pound  of  sea-water  contains  about  half  an 
ounce  of  substances  in  solution. 

46.  Experiment.  —  Pour  a  teaspoonful  of  slaked 
lime  (§  33)  into  a  bottle,  and  fill  it  with  water,  cork  it 
up,  and,  after  shaking  it  for  some  minutes,  let  it  stand 
until  the  water  has  become  perfectly  clear.  By  care- 
fully inclining  the  bottle,  most  of  the  liquid  may  be 
poured  off  free  from  the  sediment.  This  operation  is 
called  decantation,  and  the  clear  liquid  is  lime-water. 
Lime  is  but  slightly  soluble  in  water,  three  hundred 
ounces  of  water  being  required  to  dissolve  half  an  ounce 
of  lime  ;  the  excess  remains  undissolved,  and  as  lime  i? 
heavier  than  water,  it  settles  at  the  bottom.  That  a  por- 
tion of  it  has  been  dissolved  is  known  by  the  peculiar 
taste  imparted  to  the  liquid.  This  taste  is  called  alkaline. 

Keep  a  part  of  the  lime-water  in  a  well-stopped 
bottle  for  future  use;  it  will  remain  transparent  and 
clear.  Pour  the  remainder  into  a  tumbler,  and  expose 


SOLUTION    AND    CRYSTALLIZATION.  49 

• 

it  to  the  air ;  the  water  soon  becomes  turbid  and  cov- 
ered with  a  film,  which  gradually  grows  thicker,  and 
settles  at  the  bottom.  If  after  some  days  the  water 
has  become  clear  again,  it  will  have  lost  its  alkaline 
taste ;  the  lime  dissolved  in  it,  having  been  chemically 
changed  by  the  air  and  rendered  insoluble,  will  be 
found  as  a  powder  at  the  bottom  of  the  tumbler. 

47.  Experiment.  —  Put  into  a  flask  half  an  ounce  of 
litmus,  pour  over  it  three  ounces  of  water,  and  let  it 
remain  in  a  warm  place  until  the  liquid  has  obtained  a 
dark-blue  color.  Litmus  consists  of  a  blue  coloring- 
matter,  which  is  soluble  in  water,  and  is  hence  taken 
up  by  it ;  it  also  contains  some  earthy  matter,  which  is 
insoluble,  and  is  deposited  as  a  slimy  mass.  These  two 

substances  might  be  sepa- 
rated from  each  other,  as  in 
the  former  experiment,  by 
decantation,  but  it  can  be 
done  more  readily  by  filtra- 
tion. For  this  purpose,  cut 
a  piece  of  blotting-paper 
into  a  circular  shape,  fold 
it  together  twice,  and  then 
place  this  filter  into  a  glass  funnel.  That  the  paper 
and  the  glass  may  not  come  into  too  close  contact, 
place  between  them  thin  pieces  of  wood  or  glass;  a 
piece  of  cord  must  also  be  inserted  between  the  funnel 
and  the  neck  of  the  flask  into  which  the  liquid  is  to 
be  filtered,  to  allow  an  opening  for  the  escape  of  the  air 
from  the  flask,  as  otherwise  the  fluid  could  not  flow  in. 
The  filter,  which  must  never  be  higher  than  the  top  of 
the  funnel,  is  first  moistened  with  water  before  the  fluid 
is  poured  upon  it.  Blotting-paper  consists  of  fine  linen 
or  cotton  fibres  matted  together,  between  which  are 
5 


50  WATER    AND    HEAT. 

small  interstices  or  pores,  through  which  liquids,  but  nc 
tine  solid  particles,  can  pass ;  these  remain  on  the  filter 
Writing-paper  cannot  be  used  for  nitration,  as  its  pores 
are  filled  up  by  glue  or  starch. 

48.  Experiment.  —  Pour  a  part  of  the  obtained  solu- 
tion into  a  saucer,  and  pass  strips  of  fine  blotting  or  of 
letter  paper  one  or  more  times  through  it,  until  they 
have    acquired  a  distinct   blue  color.     Preserve   these 
strips,  after  being  dried,  in  a  box ;  they  are  called  blue 
litmus  or  test-paper;   they   are   reddened  by   vinegar, 
lemon-juice,  and   all  acid  fluids,   and   serve  to  test  a 
liquid,  to  ascertain   whether   it   is   acid   (has  an   acid 
reaction). 

Experiment.  —  Mix  cautiously  another  portion  of  the 
solution  with  lemon-juice,  until  the  blue  color  appears 
distinctly  red ;  this  also  serves  to  color  paper.  The  red 
test-paper  is  used  for  the  purpose  of  recognizing  a  class 
of  substances  opposed  to  acids,  that  is,  alkaline  or 
basic  bodies;  these  restore  the  original  blue  color  of 
the  paper,  as  can  be  seen  by  bringing  it  into  contact 
with  lime-water  or  moistened  ashes. 

49.  Experiment.  —  Add  gradually,  with  constant  agi 
tation,  to  one  ounce  of  cold  water,  powdered  saltpe- 
tre, as  long  as  it  continues  to  be  dissolved,  perhaps 
about  a  quarter  of  an  ounce ;  if  more  is  added  than  is 
necessary,  it  will  remain   undissolved  at  the  bottom  of 
the  vessel.     This  solution  is  said  to  be  saturated  in  the 
cold.     If  this  mixture  be  boiled,  and  saltpetre  again  be 
added,  then  about  two  ounces  more  will  be  required  to 
saturate  the  water.    A  thermometer  held  in  this  boiling 
saturated  solution  will  indicate   about  108°  C.,  while 
simple  boiling  water  indicates  only  100°  C.     All  saline 
solutions  boil  and  freeze  with  more  difficulty  than  water. 
All  bodies  soluble  in  water  behave  in  a  similar  man- 


SOLUTION  AND  CRYSTALLIZATION.          5l 


'. 


ner ;  that  is,  they  are  soluble  in  it  only  in  fixed  quanti 
ties,  and  in  most  cases  hot  water  dissolves  more  of 
them  than  cold. 

50.  Experiment.  —  If  the  solution  obtained  in  the  last 
experiment  be  poured  into  a  porcelain  dish,  previously 
heated,  and  be  sutfered  to  remain  quiet  until  cold,  then 
the  two  ounces   of   saltpetre  which   were   last    added 
separate  again,  not  as  powder,  but  as  regularly  formed 
prisms.     These  prisms  are  six-sided,  and  are  surmount- 
ed by  two  faces  similar  to  a  roof;  they  are  called  crys- 
tals of  saltpetre.    (Fig.  23.)     All  crystals  are  character- 
ized by  having  planes,  edges,  and  angles,  constructed, 
as  it  were,  of  simple  triangular,  quadrangular,  or  poly- 
angular  pieces,  artificially  polished ;  this   symmetry  is 
Fig.  23.      found  even  in  the  interior  of  them,  as  can  easi- 
ly be  seen  by   holding  a  piece  of  transparent 
crystal  towards  the  light,  and  turning  it  slowly 
round ;   or  breaking  it,  when  the  fragments  will 
often    exhibit   the    same    regular    form   which 
characterized  the  whole  crystal.     Thus  in  in- 
animate  nature  a  mysterious  power  exists,  similar  to 
that  which  compels    the  bees  to  construct   their   six- 
cornered  cells,  and  the  potato  to  produce  its  five-angled 
corolla  and  five  stamens,  and  by  which  the  smallest 
particles  of  bodies,  called  atoms,  are  forced  to  arrange 
themselves  in  a  fixed  order,  assuming  a  regular  shape. 
But  this  can  only  be  accomplished  by  a  body  in  its 
fluid  or  aeriform  state,  since  a  free  motion  of  the  atoms 
is  essential.     Time   also  is  required  for  this  operation ; 
hence  crystals  are  always  more  regular  the  more  slowly 
they  are  formed.     Many  of  the  splendid  crystals  which 
have  been  dug  from  the  depths  of  the  earth  were,- per 
haps,  thousands  of  years  in  forming. 

51.  Experiment.  —  Evaporate   the   mother-liquor   of 


52  WATER    AND    HEAT. 

the  former  experiment,  at  a  gentle  heat,  until  scales  are 
formed  on  the  surface,  then  remove  it  from  the  fire,  and 
let  the  liquid  cool,  stirring  constantly  with  a  wooden 
stick.  In  this  way,  instead  of  crystals,  a  powder  of 
saltpetre  will  be  obtained. 

The  mother-liquor,  just  alluded  to,  may  be  regarded 
as  a  cold  saturated  solution,  containing  about  a  quarter 
of  an  ounce  of  saltpetre.  If  by  evaporation  only  so 
much  water  is  left  as  is  sufficient  when  hot  to  keep  in 
solution  but  a  quarter  of  an  ounce  of  saltpetre,  then 
crystals  begin  to  appear  in  the  form  of  a  film  on  the 
colder  parts,  indicating  the  saturation  of  the  liquid.  If 
this  again  is  allowed  to  cool  quietly,  a  second  crop  of 
crystals  would  be  obtained ;  but  by  continual  stirring 
they  are  broken  at  the  moment  of  their  formation,  —  by 
slow  movement  into  a  coarse,  and  by  rapid  movement 
into  a  fine  powder.  This  may  be  called  interrupted 
crystallization.  Sugar  presents  a  similar  example ;  the 
same  syrup,  when  cooled  quietly,  yields  rock-candy ;  if 
stirred,  it  yields  common  loaf-sugar. 

52.  Experiment.  —  Put  into  boiling  water  as  much 
common  salt  as  will  dissolve,  and  let  the  solution  cool ; 
no  crystals  will  form,  because  salt  is  as  soluble  in  cold 
as  in  hot  water.     Now  evaporate  one  half  of  the  solu- 
tion over  a  spirit-lamp,  and  set  aside  the  other  half  in  a 
warm  place ;  in  the  first  case,  mere  irregular  grains  of 
salt  will  be  obtained,  but  in  the  latter  case,  after  some 
days,  regular  cubes  of  salt  will  be  deposited. 

53.  Experiment.  —  Dissolve  a  spoonful  of  salt  and  one 
of  saltpetre  in  lukewarm  water,  and  put  the  solution  in 
a  warm  place,  that  the  water  may  gradually  evaporate ; 
the  two  salts,  which  are  intimately  united  in  the  solu- 
tion, will  upon  crystallization  separate  completely  from 
each   other.    The   saltpetre  separates  into  long  prisms, 


SOLUTION    AND    CRYSTALLIZATION.  53 

• 

containing  no  trace  of  the  common  salt,  and  the  lattei 
separates  into  cubes,  entirely  free  from  saltpetre.  Thus 
the  particles  of  salt  and  saltpetre  did  not  attract  each 
other ;  but  upon  crystallizing  out  of  the  solution,  the 
homogeneous  salts  assumed  separately  a  regular  form, 
precisely  as  if  one  only  of  these  two  substances  had 
been  dissolved. 

54.  In  our  climate,  water  takes  a  solid  form  during 
the  winter  only,  and  it  is  well  known  that,  as  snow  or 
ice.  it  often  forms  the  most  regular  crystals.  But  it 
also  exists  in  a  solid  form  in  many  bodies  where  we 
should  not  expect  to  find  it ;  one  pound  of  iron-rust,  for 
example,  contains  nearly  three  ounces,  and  one  pound 
of  slaked  lime  four  ounces,  of  water,  and  yet  both  are 
apparently  dry.  This  water  is  said  to  be  chemically 
combined.  It  also  unites  with  other  solid  bodies,  for 
which  it  has  an  affinity.  Such  combinations  of  solids 
with  water  are  called  hydrates.  It  is  also  frequently 
present  in  salts,  as  can  be  shown  in  a  simple  manner  in 
the  case  of  the  well-known  Glauber  salts. 

Experiment.  —  Place  half  an  ounce  of  crystallized 
Glauber  salts  in  a  warm  place,  when  it  will  soon  lose 
its  transparency,  and  finally  crumble  into  a  white 
powder,  weighing  hardly  a  quarter  of  an  ounce.  That 
which  has  been  lost  was  water,  and  it  is  evident  that  it 
was  this  water  which  gave  to  the  salt  its  crystalline 
form  and  transparency,  these  both  vanishing  with  the 
escape  of  the  water.  For  this  reason  the  water,  on 
which  depends  the  crystalline  form  of  many  salts,  is 
called  the  water  of  crystallization.  Saltpetre  and  com- 
mon salt,  treated  like  Glauber  salts,  lose  nothing  in 
weight,  neither  do  they  become  opaque  nor  pulverulent 
they  contain  no  chemically  combined  water. 
5* 


54 


WATER    AND    HEAT. 


Fig.  24. 


COMPOSITION  OF  WATER. 

55.  Besides  that  electricity,  which  we  admire  on  a 
grand  scale  in  the  majestic  phenomena  of  lightning, 
or  which  we  generate  on  a  small  scale  by  rubbing 
various  bodies  together,  a  second  kind  of  electricity  is 
also  recognized,  which  is  called  galvanic  force,  or  gol~ 
vanism.  This  has  attained  great  importance  in  chem- 
istry, as  by  means  of  it  the  chemist  is  enabled  to  de- 
compose almost  all  chemical  combinations,  even  into 
their  component  parts  or  chemical  elements.  By  gal- 
vanic force  water  can  easily  be  decomposed  into  its  ele- 
mentary parts.  This  sort  of  electricity  may  be  gener- 
ated in  various  ways ;  it  is  developed  in  every  chemical 
combination  or  decomposition,  indeed 
quite  frequently  when  heterogeneous 
substances,  whether  solid,  liquid,  or 
aeriform,  are  brought  into  contact. 
The  oldest  and  most  common  gal- 
vanic apparatus  is  the  voltaic  pile, 
in  which  electricity  is  excited  by 
the  contact  of  two  different  metals, 
commonly  zinc  and  copper.  A  cop- 
per plate  placed  upon  one  of  zinc  is 
called  a  pair  of  plates;  many  such 
pairs  are  laid,  one  above  the  other, 
each  pair  being  separated  by  a  piece 
of  cloth  moistened  with  salt  water. 
The  relative  position  of  the  met- 
als in  each  pair  must  be  observed 
throughout  the  whole  series,  so  that, 
if  the  pile  commences  with  a  zinc 
plate,  it  shall  terminate  with  a  cop- 
per one.  These  two  extremities  are 


COMPOSITION    OF    WATER.  56 

called  the  pole&.  Zinc  is  called  the  -j-  pole,  and  copper 
the  —  pole ;  they  are  provided  with  metallic  wires,  that 
the  electric  or  galvanic  stream  which  is  excited  in  the 
pile  may  be  conveyed  to  any  place  desired.  When 
the  two  ends  of  the  wires  are  brought  very  near  to  each 
other,  sparks  are  seen  to  dart  from  one  to  the  other ; 
this  is  a  token  of  the  galvanic  current,  manifesting  itself 
in  the  same  manner  as  the  current  of  the  electrical  ma- 
chine. 

To  decompose  water  by  means  of  this  pile,  the  twc 
wires,  being  previously  tipped  with  platinum,  are  con- 
ducted into  a  vessel  of  water,  and  two  test-tubes,  filled 
with  water,  are  inverted,  one  over  the  end  of  each  wire ; 
there  are  evolved  from  the  ends  of  both  wires  small 
bubbles  of  air,  which  ascend  into  the 
test-tubes,  gradually  displacing  the  water 
from  them.  From  the  -j-  or  zinc  wire, 
only  half  as  much  gas  is  generated  as 
from  the  other;  consequently  the  tube 
connected  with  the  zinc  will  only  be  half 
emptied  by  the  time  the  water  from  the 
other  is  entirely  expelled,  and  a  glowing 
shaving  introduced  into  it  will  burst  into 
a  brilliant  flame  ;  it  is  called  oxygen  gas  ( O).  The  gas 
evolved  from  the  —  or  copper  end,  on  the  contrary,  ex- 
tinguishes this  shaving;  but  the  gas  will  burn  spon- 
taneously if  kindled  by  the  flame  of  a  lamp,  held  over 
it;  —  it  is  called  hydrogen  gas  (H).  These  are  the 
component  parts  of  water;  it  consists  of  one  measure 
(volume)  of  oxygen,  and  of  two  measures  of  hydrogen. 
From  one  measure  of  water,  when  decomposed  into  its 
elements,  several  thousand  measures  of  these  two  gases 
may  be  obtained.  J 


56 


METALLOIDS. 


Fig.  26. 


NON-METALLIC   ELEMENTS,   OR   METAL- 
LOIDS. 

FIRST   GROUP:   ORGANOGENS. 

OXYGEN  (0). 
At.  Wt.=  100.  —  Sp.  Gr.  =  l.l. 

56.  OXYGEN  may  be  obtained  in  great  quantities 
from  water,  by  means  of  the  galvanic  battery ;  but  in  a 
more  simple  manner  as  follows. 

Experiment.  —  Introduce  into  a  somewhat  tall,  but 

not  too  thin,  test- 
tube,  109  grains 
of  red  oxide  of 
mercury.  One 
end  of  a  bent 
glass  tube  is 
adapted  to  it  by 
means  of  a  per- 
forated cork,  and 
the  other  end  is 
conducted  into  a 
vessel  filled  with 
water.  Either 
suspend  the  tube 
by  means  of  a 
piece  of  cord  or  wire,  or  support  it  by  a  retort-holder. 
A  retort-holder  is  a  wooden  stand  provided  with  a  mov- 
able vice,  by  which  glass  vessels  can  be  held  in  the 
most  convenient  manner,  as  shown  in  the  annexed 
figure.  Then  heat  the  test-tube  until  all  the  oxide  of 
mercury  has  disappeared.  The  red  powder  becomes 
black  as  the  heat  increases,  and  bubbles  of  air  escape, 
which  are  collected  in  a  glass  bottle  held  over  the  end 


OXYGEN.  5"* 

- 

of  the  tube,  this  bottle  having  been  previously  filled 
with  water  and  then  inverted  into  the  bowl,  after  clos- 
ing the  mouth  of  it  with  the  finger  or  a  glass  plate. 
No  water  will  escape  until  bubbles  of  air  from  the  tube 
are  passed  into  it,  which,  on  account  of  their  greater 
levity,  ascend  and  displace  the  water.  When  the  water 
is  displaced,  remove  the  bottle  and  close  it  with  a  cork, 
replacing  it  with  another  bottle,  likewise  previously 
filled  with  water,  and  repeat  this  process  until  the 
evolution  of  gas  ceases.  The  first  bubbles  that  pass 
over  consist  of  atmospheric  air  contained  in  the  test- 
tube,  but  the  oxygen  gas  quickly  succeeds.  This  is 
one  of  the  component  parts  of  the  red  oxide  of  mercury, 
and  can  easily  be  recognized  by  the  vivid  combustion 
in  it  of  a  glowing  shaving.  At  the  same  time  there  is 
formed  on  the  upper  part  of  the  test-tube  a  brilliant 
metallic  mirror,  which  consists  of  mercury,  the  second 
element  of  the  red  oxide.  When  the  latter  has  entire- 
ly disappeared,  immediately  withdraw  the  tube  from 
the  water,  let  the  test-tube  cool,  and  unite  the  mercury 
adhering  to  its  walls  into  a  single  globule,  by  means 
of  a  feather.  It  will  amount  in  weight  to  101  grains  ; 
this,  subtracted  from  the  original  weight,  109  grains, 
leaves  8  grains,  the  amount  of  the  oxygen.  The  red 
powder  consists  of  a  brilliant  heavy  metal  and  of  a 
gas,  two  entirely  dissimilar  bodies.  If  these  are  chem- 
ically combined  together  by  proper  means,  they  will 
unite  again  to  a  red  oxide,  a  body  in  which  the  pecu- 
liar properties  of  mercury  as  well  as  of  oxygen  are  en- 
tirely lost. 

57.  This  experiment  shows,  also,  how  the  force  of 
heat  alone  can  destroy  a  chemical  combination,  or  in 
othor  words  the  affinity  of  two  bodies  for  each  other 
This  can  be  explained  as  follows.  Chemical  affinity 


'r>8  METALLOIDS. 

nets  only  at  imperceptible  distances,  consequently  onty 
when  bodies  are  in  closest  contact ;  heat  counteracts 
this  power,  for  it  exerts  an  expansive  action,  and  conse- 
quently separates  the  constituent  particles  from  each 
other.  In  the  cold,  or  at  ordinary  temperatures,  the 
single  particles  of  the  quicksilver  (Q)  and  oxygen  (O) 
are  so  closely  united,  that  chemical 
force  is  sufficient  to  hold  them  to- 
gether (a,  Fig.  27) ;  but  at  an  increased 
temperature  they  are  so  far  separat- 
ed (6),  that  the  influence  of  chem- 
ical attraction  is  overcome.  This  occurs  so  much  the 
more  readily  in  this  instance,  as  both  the  quicksilver 
and  oxygen,  having,  when  heated,  a  strong  tendency  to 
become  aeriform,  help  likewise  to  counteract  the  chem- 
ical force. 

58.  The  bottles  containing  the  oxygen  appear  to  be 
empty,  for  oxygen  is  as  colorless  and  invisible  as  com- 
mon air,  and  is  without  odor  or  taste.  In  German  it 
is  caUed  Sauerstoffluft,  signifying  sour  gas. 

Experiment.  —  Introduce  a  glowing  shaving  into  a 
bottle  of  oxygen;  it  will  kindle  and  burn  for  some 
time  with  great  brilliancy  and  a  very  dazzling  flame, 
and  then  be  extinguished.  The  same  takes  place  when 
a  piece  of  lighted  tinder  is  affixed  to  a  wire  and  sus- 
pended in  the  oxygen ;  the  tinder  burns  with  a  lively 
flame,  while,  as  is  well  known,  it  merely  smoulders 
away  in  the  open  air.  Oxygen  possesses,  at  a  high 
temperature,  a  strong  affinity  for  the  component  parts 
of  wood  and  tinder;  that  is,  it  combines  with  them  with 
great  energy,  and  consequently  with  the  development 
of  heat  and  light.  When  the  combination  has  ended, 
and  the  oxygen  is  consumed,  the  combustion  ceases. 
The  product  of  the  combustion,  that  is,  the  combina 


OXYGEN.  59 

tion  of  the  wood  with  the  oxygen,  is  also  aeriform ;  but 
burning  substances  are  extinguished  in  the  newly 
formed  gas.  If  the  bottle  be  rapidly  whirled  round,  the 
gas  formed  by  the  combustion  will  escape,  and  atmos- 
pheric air  will  supply  its  place.  Air  contains  free  oxy- 
gen ;  and  a  kindled  shaving  will  burn  in  it  for  some 
time,  but  far  slower  and  less  briskly  than  in  pure  oxy- 
gen ;  because  common  air  contains  only  one  fifth  part 
of  oxygen.  Accordingly,  a  combustion  in  oxygen  pro- 
ceeds five  times  more  rapidly  and  violently  than  in  at- 
mospheric air. 

59.  Experiment.  —  To  prepare  a  larger  quantity   of 
oxygen,  take  one  hundred  grains  of  chlorate  of  potassa, 
and  heat  it  in  the  same  manner  as  described  in  the 
former  experiment ;  the  salt  will  soon  melt,  and  after- 
wards boil.     As  soon   as  the   boiling  commences,  the 
flame  must  be  diminished,  to  prevent  the  mass  from 
foaming  over.     When   the  liquid  thickens,  if  some  of 
the  substance   should  be  found  adherent  to  the  colder 
parts  of  the  test-tube,  approach  it  with  the  flame  of  the 
lamp,  until  it  is  again  melted  down.     As  soon  as  the 
gas  ceases  to  be  generated,  draw  the  tube  immediately 
from  the  water.     If  you  mix,  by  merely  rubbing  together 
with  the  fingers  upon  a  sheet  of  paper,  chlorate  of  potas- 
sa  with  its  own  weight  of  black  oxide  of  manganese, 
the  evolution  of  gas  will  be  vastly  accelerated. 

60.  For  collecting  gases  in  larger  quantities,  the  fol- 
owing  contrivance  may  be  resorted  to.     Make  a  shelf 

Fjo,  2g  out    of  slate  or  a  piece  of  lead, 

some  inches  broad,  and  so  long 
that  it  will  rest  about  half  way  up 
the  sloping  walls  of  the  vessel  in 
which  it  is  to  be  placed;  bore  a 
small  hole  through  the  centre  of 
the  shelf  with  some  appropriate 


60  METALLOIDS. 

instrument.  When  wanted  for  use,  pour  into  the  vessel 
as  much  water  as  will  be  sufficient  to  cover  the  shelf  an 
inch  deep,  and  then  invert  the  vessel  intended  for  the 
reception  of  the  gas,  with  its  mouth  exactly  over  the 
opening,  placing  the  extremity  of  the  glass  tube,  from 
which  the  gas  proceeds,  directly  beneath,  so  that  the  gas 
may  enter  it  as  through  a  funnel.  This  contrivance  is 
called  a  pneumatic  trough.  In  order  to  coUect  and  pre- 
serve larger  quantities  of  gas,  and  to  experiment  with 
them  more  conveniently,  special  contrivances,  called 
gasometers^  are  used  in  chemical  laboratories. 

61.  Chlorate  of  potassa  contains  for  every  one  hun- 
dred  grains   about  forty  grains  of  oxygen  chemically 
combined ;  by  the   application   of  heat,  these  become 
free  and  escape.     Red  oxide  of  mercury  contains  only 
eight  per  cent,  of  oxygen  ;   therefore  the  former  will 
yield  five  times  more  oxygen  than  the  latter.     If  vials 
of  twelve  ounces'  capacity  are  selected  for  receiving  the 
gas,  we  shall  be  able  to  fill  five  of  them,  and  shall  have 
in   each  about  eight   grains,   or   nearly  twenty  cubic 
inches,  of  oxygen. 

Chlorate  of  potassa  may,  under  some  circumstances, 
as  when  strongly  rubbed,  or  treated  with  sulphuric 
acid,  occasion  very  dangerous  explosions ;  but  no  dan- 
ger is  to  be  apprehended  from  the  application  of  it, 
when  made  as  above  directed. 

62.  Experiment.  —  Add  warm  water  to  the  salt  re- 
maining in  the  test-tube  after  the  expulsion  of  the  oxy- 
gen, and  place  the  tube  in  a  warm  place  until  the  salt 
is  dissolved ;  evaporate  the  solution  gradually,  over  a 
stove,  when  small   cubic  crystals   (chloride   of  potas- 
sium) will  be  deposited.     The  chlorate  of  potassa  crys- 
tallizes in  thin  tables   or  plates,  the  heated  mass  in 
cubes ;  this  difference  in  the  form  of  the  crystals  alone 
indicates  that,  by  the  heating  of  the  former,  an  entirely 


OXYGEN.  61 

new  salt  is  formed,  and  one,  indeed,  which  no  longer 
contains  oxygen.  The  following  diagram  will  illus- 
trate this  more  clearly. 

Chlorate  of  potassa  consists  of 

Ch loric  $  Oxygen Oxygen 

Acid     I  Chlorine  ____^^^         (escapes  as  gas.) 

ana     ^  Oxygen— - — "        ____^- — Chloride  of  potassium 
Potassa  (  Potassium  —  (remains  in  the  tube.) 

Experiments  with  Oxygen. 

63.  Experiment  a.  —  Fasten  a  piece  of  charcoal  to  a 
wire,  and  kindle  it  in  the  flame  of  a  lamp,  and  then  in- 
troduce it  into  a  bottle  of  oxygen ;   it  will  burn  very 
vividly,  and   with  a   flame.     If  .a  piece   of  moistened 
blue  litmus-paper  (§  48)  be  introduced  into  the  bottle, 
after  the  combustion,  it  will  be  reddened ;  consequently 
an  acid  gas  has  been  formed  from  the  charcoal  and  the 
oxygen;   it  is  called  carbonic   acid.     Close   the  flask, 

nake  it  a  few  times,  and  place  it  aside. 

64.  Experiment  b.  —  If  some  pieces  of   sulphur  are 

fastened  to  a  longer  wire,  kindled  and  sus- 
pended in  a  second  bottle,  they  will  burn 
with  a  beautiful  blue  flame.  The  gas 
formed  from  this  union  of  sulphur  and 
oxygen  has  a  very  irritating  odor ;  it  like- 
wise turns  litmus-paper  red,  and  conse- 
quently it  is  of  an  acid  nature.  It  is  called 
sulphurous  acid.  This  bottle  is  also  closed 
and  preserved  for  future  use. 

65.  Experiment  c.  —  Take   a   small   piece   of   phos- 
phorus, which,  on  account  of  its  inflammability,  must 
be   cut  off  under  water  from  the   stick,   and  place  it, 
after  having  been  well  dried  between  blotting-paper 

6 


62 


METALLOIDS. 


Fig.  30. 


in  a  scooped-out  piece  of  chalk.  Fasten 
the  latter  to  a  wire,  and  introduce  it  into  a 
third  flask  of  oxygen.  Affix  the  wire  to  a 
transverse  piece  of  wood,  so  that  the  chalk 
may  hang  a  little  below  the  centre  of  the 
bottle.  If  the  phosphorus  be  now  touched 
with  a  hot  wire,  it  will  kindle-  and  burn 
with  a  dazzling  brilliancy,  filling  the  bottle 
with  a  thick  white  smoke.  This  smoke  consists  of  a 
chemical  combination  of  oxygen  and  phosphorus;  it 
reddens  the  blue  test-paper,  consequently  is  also  an 
acid;  it  is  called  phosphoric  acid.  If  the  bottle  be 
allowed  to  stand  for  a  time,  the  smoke  will  sink  to  the 
bottom,  and  dissolve  in  the  water  previously  put  there, 
which  thus  acquires  an  acid  taste. 

66.  In  the  same  way  as  the  tasteless  coal  and  sul- 
phur and  the  phosphorus  acquire,  by  combination  with 
oxygen,  acid  properties,  so  many  other  simple  bodies 
are  converted  by  oxygen  into  acids ;  this  is  the  reason 
why  it  has  received  the  name  oxygen,  derived  from  two 
Greek  words,  one  of  which  signifies  acid,  and  the  other 
to  generate.  Thence  the  words  oxidate  and  oxide,  so 
frequently  occurring  in  chemistry.  Oxidate  signifies  to 
unite  with  oxygen,  to  burn ;  oxide  is  the  product  of  the 
combination  and  signifies  a  burnt  substance,  that  is,  a 
substance  combined  with  oxygen.  The  acids 
just  alluded  to  may  also  be  called  acid  oxides. 
67.  Experiment  d.  —  Fix  securely  to  a 
wire  a  piece  of  sodium,  and  let  it  remain 
for  some  hours  in  a  bottle  filled  with  oxy- 
gen ;  it  becomes  converted  into  a  white 
mass,  which  easily  dissolves  in  water.  The 
solution  obtained  has  an  alkaline  taste, 
similar  to  lime-water;  the  color  of  blue 


Fig.  31. 


OXYGEN.  63 

*** 

test-paper  is  not  changed  by  it,  but  it  turns  red  test- 
paper  blue;  this  is  a  combination  which  may  be  re 
garded  as  the  opposite  of  acids ;  it  is  called  oxide  of 
sodium.     Let  this  also  be  kept  for  future  use. 

The  metal  sodium  has  such  an  extraordinary  affinity 
for  oxygen,  that  it  quickly  attracts  it  from  the  air. 
Therefore,  to  preserve  it  unchanged,  it  must  be  kept  in 
some  liquid  containing  no  oxygen  ;  as,  for  instance,  in 
naphtha  or  petroleum. 

68.  Experiment  e.  —  A  piece  of  fine  iron  wire  is  so 

wound  round  a  slate  or  common  lead  pen- 
cil, that,  on  the  withdrawal  of  the  latter,  the 
wire  may  have  a  spiral  form.  Fasten  the 
upper  part  of  this  wire,  as  in  experiment  c, 
to  a  cross-piece  of  wood,  and  place  on  the 
lower  end  of  it  a  small  portion  of  tinder. 
When  this  is  kindled,  introduce  the  wire 
into  the  oxygen;  the  burning  tinder  heats 
the  iron  to  redness,  which  then  burns  brilliantly,  throw- 
ing out  sparks.  The  iron,  when  red-hot,  combines 
with  the  oxygen.  The  burnt  or  oxidized  iron  (iron 
scales)  melts,  and  falls  to  the  bottom  in  globules, 
which  are  so  hot  that  they  are  liable  to  melt  into  the 
glass,  though  it  be  partly  filled  with  water.  This 
heat,  as  in  the  preceding  case,  is  the  result  of  chemical 
combination  taking  place.  Oxide  of  iron  is  insoluble 
in  water,  and  for  this  reason  it  affects  the  color  neither 
oi  the  blue  nor  of  the  red  test-paper ;  if  it  were  soluble, 
it  would,  like  oxide  of  sodium,  convert  the  red  into 
blue  paper. 

69.  Such   combinations  of  oxygen  as  are  not  acid, 
but  agree  in  their  properties  with  the  oxide  of  sodium 
or  of  iron,  are  called  bases  or  basic   oxides.     Most  of 
the  combinations  of  the  metals  with  oxygen  belong  to 
the  bases 


64 


METALLOIDS. 


70.  By  the  foregoing  experiments  on  oxidation,  tht 
question   recurs,  —  How   much    carbon,   sulphur,   &c., 
have  the  eight  grains  of  oxygen    contained  in    each 
bottle  consumed  or  taken  up  ?     The  reply  is,  —  They 
have  taken  up  different  quantities. 

They  have  united  as  follows:  — 

8  grs.  of  oxygen  with  3  grs.  of  carbon,  forming  1 1  grs.  of  carbonic  acid. 
8       "          M          "     8      "      sulphur,        "16        "  sulphurous  acid 
8       "          "          «     6i     "      phosphorus,  "      14i      "  phosphoric  acid. 
8       "          «         "23      "     sodium,         "     31        "  oxide  of  sodium. 
8       "          "          "  20      "      iron,  "     28        "  black  oxide  of  iron. 

8       "          "         "     1       "      hydrogen,     «       9        "  oxide  of  hydrogen 

(water). 

Carbonic  acid  may  be  prepared  in  different  ways,  but 
it  is  always  so  constituted  as  to  contain  eight  grains  oi 
oxygen  united  with  three  grains  of  carbon,  and  this 
same  regularity  exists  in  all  the  above  compounds,  as 
indeed  in  all  chemical  combinations.  It  is  a  law  of 
nature ;  chemical  combinations  always  take  place  accord- 
ing' to  certain  fixed  proportions  by  measure  or  weight. 
This  doctrine  is  called  Stochiometry  (from  o-rotxetoi/,  ele- 
ment, and  pfTpov,  measure). 

71.  Experiment. —  The  liquid    in   the  vessel  c  red- 
dened blue  test-paper,  and  had  a  sour  taste ;  the  liquid 
in  the  vessel  e?,  on  the  contrary,  turned  the  red  paper 
blue,  and  had  an  alkaline  taste.    Add  the  latter  slowly, 
and  at -last  only  by  drops,  to  the  former,  testing  the 
mixture  frequently  with  a  strip  of  blue  and  of  red  test 
paper ;  there  will  be  a  point  when  the  color  of  these 
two  papers  will  no  longer  be  changed.     The  acid  and 
alkaline  tastes  have  likewise  disappeared,  and  the  mix- 
ture has  acquired  a  slightly  saline  taste;  it  is  neutral. 
The  phosphoric  acid  has   chemically  combined   with 
the   oxide   of  sodium,  forming  a  new  body  having  no 
similarity  to  either  of  the  substances  of  which  it  waa 


OXYGEN.  65 

composed.  To  obtain  a  better  knowledge  of  it,  let  the 
vessel  remain  in  a  warm  place  until  the  water  haft 
evaporated,  when  small  crystals  will  be  deposited. 
Such  a  combination,  consisting  of  an  acid  and  a  base, 
is  called  a  salt.  This  salt,  phosphate  of  soda,  is  called 
soluble,  because  it  assumes  a  liquid  form  upon  the  ad- 
dition of  water. 

72.  Experiment.  —  Pour  into  the  bottle  which  con- 
tained the  carbonic  acid   gas   (experiment  63),  some 
lime-water  (§  46),  and  agitate  it ;  the  liquid  will  be- 
come milky,  and  after  standing,  a  white  powder  will 
subside.     The  lime  in  the  lime-water  is  a  base,  as  well 
as  the  oxide  of  sodium ;  the  lime  combines  with  car- 
bonic acid,  they  mutually  neutralizing  each  other  ;  but 
the  salt  which  is  formed  (carbonate  of  lime  or  artificial 
shalk)  is  insoluble  in  water,  and  hence  separates  from  it. 
That  the  carbonic  acid   here  disappears,  and  is  con- 
densed into  a  solid  body,  is  indicated  by  the  suction 
exerted  upon  the  finger  with  which  the  mouth  of  the 
bottle  was  closed  during  the  shaking,  and  the  rushing 
in  of  air  after  its  removal. 

73.  Experiment.  —  Quite    the    same    thing    occurs, 
when  lime-water  is   poured  into  the  bottle  of  experi- 
ment 64;   the  irritating   odor  of  the  sulphurous  acid 
contained  in  it  vanishes,  owing  to  its  combining  with 
the  lime.     The  salt  formed  (sulphite  of  lime)  is  diffi- 
cultly soluble  in  water. 

74.  Experiment.  —  Pour  gradually  into  the  bottle  of 
experiment  68,  one  dram  of  common  sulphuric  acid. 
It  heats  on  uniting  with  the  water ;  and,  after  repose 
and  frequent  agitation,  the  red  oxide  of  iron  which  col- 
lects on  the  sides  of  the  vessel,  as  well  as  the  black 
oxide  of  iron  at   the  bottom,  will  dissolve.     In   this 
case,   also,  a  salt  is  formed,  since  the  base   (oxide  of 

6* 


66  METALLOIDS. 

iron)  has  united  chemically  with  the  acid ;  the  yellow- 
ish liquid  holds  the  iron  salt  in  solution. 

75.  Degrees  of  Oxidation.  —  Oxygen  is  a  universal 
food  for  all  elements  ;  it  is  consumed  by  them,  and,  as 
already  stated,  in  fixed  quantities.     But  the  appetite  of 
an   element  for  oxygen  often  varies  according  to  the 
circumstances   under  which   the  latter  is  presented  to 
it ;  for  example,  it  is  greater  under  the  influence  of  heat 
than  of  cold,  greater  where  there  is  an   excess  than 
where  there  is  a  deficiency  of  oxygen.     Hence  many 
elements  frequently  consume  greater  quantities  of  it  at 
a  high  than  at  a  low  temperature,  and  when  the  sup- 
ply is  copious  than  when  it  is  deficient ;  and  this  ex- 
cess or  diminution    of  consumption   is   likewise   pre- 
scribed by   fixed  laws.     The   different  proportions  in 
which  substances  unite  with  oxygen  are  called  its  de- 
grees of  oxidation.     (See  p.  682.) 

76.  When  sulphur  is  burnt  in  oxygen  gas  or  in  the 
air,  it  combines  with  oxygen,  forming  sulphurous  acid; 
but  when  it  unites  with  one  half  as  much  more  oxygen, 
sulphuric  acid  is  formed. 

When  phosphorus  is  rapidly  burnt,  it  forms  with 
oxygen  phosphoric  acid;  but  if  it  be  exposed  to  the  aii 
without  the  application  of  heat,  or  be  burnt  with  im- 
perfect access  of  air,  then  phosphorous  acid  is  princi- 
pally formed,  which  contains  two  fifths  less  oxygen 
than  phosphoric  acid. 

Accordingly,  by  the  terms  sulphuric  and  phosphoric 
acids,  are  to  be  understood  combinations  with  more 
oxygen  ;  by  the  terms  sulphurow-s  and  phosphorous 
acids,  combinations  with  less  oxygen.  If  an  element 
yields  more  than  two  acids  with  oxygen,  then  new 
names  are  formed  by  prefixing  to  the  acids  the  terms 
per  or  hypo ;  for  instance,  perchloric  acid,  hyposulphuric 
and  hyposulphurous  acids,  &c. 


OXYGEN.  67 

•V 

77.  Besides  ttie  red  oxide  or  peroxide  of  quicksilvei 
(§56)  there  is  yet  another  combination  of  quicksilver 
with  oxygen,  which  is  black,  and  contains  only  half  as 
much  oxygen  as  the  former;   it  is  called  the  protoxide 
of  quicksilver.     Iron  also  forms  two  combinations  with 
oxygen;   one  of  a  reddish-brown  color  (sesquioxide  of 
iron),  and  the  other  of  a  black  color,  containing  one 
third  less  oxygen  (protoxide  of  iron).     Accordingly  a 
peroxide  or  a  sesquioxide  is  the  combination  of  a  metal 
with  a  greater  quantity  of  oxygen,  and  a  protoxide  is  a 
combination  with  a  less  quantity  of  oxygen.      Many 
metals  have  the  power  of  uniting  in  more  than  these 
two  proportions  with  oxygen ;  in  this  case,  the  combi- 
nation with  a  less  quantity  of  oxygen  than  in  the  pro- 
toxide is  called  suboxide,  but  that  with  more  oxygen 
than  in  the  per-  or  sesqui-oxide,  is  called  hi/peroxide. 
Neither  the  lower  nor  the  higher  oxides  act  as  bases, 
that  is,  they  will  not  unite  directly  with  acid?  to  form 
salts ;  but,  nevertheless,  this  may  happen  when  the  sub- 
oxide  receives  so  much  oxygen,  or  the  hyperoxide  parts 
with  so  much,  as  to  form,  in  either  case,  per-  or  sesqui- 
oxides  or  protoxides.      Some  metals  in  their   highest 
state  of  oxidation  possess  no  longer  basic  properties, 
but,  on  the  contrary,  acid  properties  (metallic  acids). 

78.  If  we  compare  the  different  quantities  of  oxygen 
which  one  and  the  same  body  can  take  up,  they  will 
always  be  found  in  very  simple  proportions;   for  in- 
stance :  — 

[n  sulphurous  and  sulphuric  acids,     as  2  to  3. 

"   phosphorous  and  phosphoric  acids,    "  3  to  5. 

"   protoxide  and  peroxide  of  mercury,  "  1  to  2. 

"    protoxide  and  sesquioxide  of  iron,    "  2  to  3. 

A  similar  regularity  exu  ts  in  all  other  chemical  com 

binations. 


METALLOIDS. 

79.  The  hi/peroxides  easily  give  up  a  part  of  their  ox 
ygen,  either  when  heated  alone  or  with  certain  acids  • 
hence  they  can  be  made  use  of  for  obtaining  oxygen 
An  oxide  of  frequent  occurrence  in  nature  is  the  hy~ 
peroxide  of  manganese,  used  for  coloring  potters'  ware 
brown.     It  is  a  combination  of  the  metal  manganese 
with  oxygen.     Oxygen  is  usually  obtained  from  this 
when  wanted  in  large  quantities,  as  it  can  be  put  in  an 
iron  vessel   and   heated  to  a  bright  redness.     If  the 
manganese  is  heated  alone,  one  third  of  the  oxygen 
contained  in   it  is  obtained,  and   red   oxide  of  man- 
ganese remains  behind ;  but  if  heated  with  the  addi- 
tion of  sulphuric  acid,  one  half  of  its  oxygen  is  ob- 
tained, and  the  remainder  is  protoxide  of  manganese, 
which  combines  with  the  sulphuric  acid,  forming  a  salt. 

80.  Oxygen  is  absolutely  necessary  to  all  living  crea- 
tures.    All  the  air  which  we  breathe  must  contain  free 
oxygen;    if   this   is   wanting,   suffocation   is   induced. 
The  chemists  who  discovered  it  seventy  years  ago,  and 
first  prepared  it  pure,  gave  to  it,  for  this  reason,  the 
name  of  vital   air.     In  later  times  it  was  designated 
empyreal  air,  because  it  was  found  that  every  combus- 
tion, however  familiar  to  us,  was  a  process  of  oxida- 
tion, in  which  the  oxygen  of  the  air  combined  with  the 
particles  of  the  burning  material.     The  symbol  for  ox- 
ygen is   O,   the  first  letter  of  oxygen.      It   has   been 
agreed  to  express  simple  bodies  by  the  first  letters  of 
their  Latin  names. 

HYDKOGEN  (H). 
At.  Wt.  =  12.5.  —  Sp.  Gr.  =  0.068. 

81.  Experiment.  —  Boil  some  water  for  fifteen  min- 
utes, that  all  the  air  contained  in  it  may  be  expelled ;  let 


HYDROGEN.  69 

it  cool,  and  iill  a':bowl  and  a  test-tube  with  it ;  close  the 
Fjnr  33  latter  with  the  finger,  and  invert  it  under 

^       the  water  in  the  bowl.     Now  secure  to 
N.  f       a  wire  a  piece  of  sodium,  of  the  size  of 

a  lentil,  and  thrust  it  quickly  under  the 
opening  of  the  test-tube ;  the  metal 
frees  itself  from  the  wire,  and,  as  it  is 
lighter  than  water,  it  ascends  into  the 
tube,  floating  there  with  a  circuitous  motion ;  a  gas  is 
evolved  from  the  water,  which  in  a  few  moments  be- 
comes displaced  by  the  gas  from  the  tube.  This  kind 
of  gas  is  the  second  element  of  water,  and  is  called 
hydrogen.  The  experiment  in  §  67  demonstrates  that 
sodium  has  a  very  great  affinity  for  oxygen,  and  this 
affinity  is  so  strong,  that  the  sodium  removes  from  the 
water  its  oxygen,  whereby  the  hydrogen  is  liberated. 
Close  the  tube  again  with  the  finger,  remove  the  tube 
from  the  vessel,  and  hold  a  burning  taper  over  it,  when 
the  gas  will  burn  with  a  flame.  Hydrogen  is  a  com- 
bustible gas.  If  the  interior  of  the  moist  tube  be  tested 
with  a  strip  of  red  test-paper,  this  assumes  a  blue  color. 
The  same  base,  oxide  of  sodium,  has  been  formed  as 
when  the  sodium  was  exposed  to  oxygen  or  to  the  air. 
It  is  dissolved  by  the  water. 

82.    What   sodium  accomplishes  at  ordinary   tem- 


peratures, iron  cannot  do  until  it  is  heated  to  redness 


70  METALLOIDS. 

Pass  water  in  the  form  of  steam,  obtained  by  boiling 
the  water  in  the  retort,  a  (Fig.  34),  through  a  red-hot 
iron  pipe  containing  a  spiral  wire ;  for  instance,  a  gun- 
barrel.  At  this  high  temperature  the  iron  in  the  pipe 
unites  with  the  oxygen  in  the  water,  forming  black  ox- 
ide of  iron,  and  the  hydrogen  is  set  free.  This  is  the 
method  by  which  the  celebrated  French  chemist,  Lavoi- 
sier, sixty  years  ago,  proved  that  water  is  not  a  simple 
body,  but  consists  of  two  gases,  oxygen  and  hydrogen. 

83.  The  decomposition  of  water  by  iron  is  more  ea- 
sily effected  through  the  presence  of  an  ally,  which  sup- 
ports the  iron  in  its  endeavour  to  extricate  the  oxygen 
from  the  water.  Such  an  ally  is  sulphuric  acid. 

Experiment.  —  Put  a  quarter  of  an  ounce  of  wrought- 
Fj(r  35  iron   filings  into  a  flask, 

and  pour  over  them  two 
and  a  half  ounces  of  wa- 
ter. No  action  takes  place, 
but  if  half  an  ounce  of 
common  sulphuric  acid  be 
gradually  added,  at  the 
same  time  keeping  the 
flask  in  constant  motion,  ebullition  and  heating  of 
the  liquid  will  immediately  ensue.  The  ebullition  is 
caused  by  the  evolution  of  a  species  of  gas,  hydrogen. 
Insert  into  the  opening  of  the  flask  a  perforated  cork,  to 
which  is  fitted  a  bent  glass  tube.  Allow  the  first  por- 
tions of  the  gas  to  escape,  then  collect  it,  as  the  oxygen 
was  collected,  in  a  flask  filled  with  water  over  the 
pneumatic  trough. 

There  is  one  indispensable  caution  to  be  observed  in 
experimenting  with  hydrogen,  which  is,   not  to   admit 
the  gas  into  the  receiver  until  all  the  atmospheric  air  ex- 
isting- in  the  flask  has  been  expelled^  as  otherwise  an  ex 
plosion  might  take  place. 


HYDROGEN. 


71 


Fig.  36. 


84.  Experiment.  —  If  sulphuric  acid  is  poured  into 
water,  considerable  heat  is  evolved ; 
but  this  heat  is  much  stronger  when 
the  water  is  poured  into  the  sulphu- 
ric acid.  The  mixture  is  best  made 
in  the  following  manner.  Pour  two 
and  a  half  ounces  of  water  into  a 
sufficiently  large  stone  jar,  which  is 
placed  in  a  bowl  filled  with  water ;  now  weigh  in  a 
flask  half  an  ounce  of  common  sulphuric  acid,  pour  this 
in  a  small  stream  into  the  water,  stirring  the  water  con- 
tinuously with  a  glass  or  porcelain  rod,  and  let  the  jar 
remain  in  the  bowl  until  it  is  entirely  cold.  This  mix- 
ture is  called  dilated  sulphuric  acid ;  the  strong  acid,  on 
the  contrary,  is  called  concentrated  sulphuric  acid. 


Fig.  37. 


85.  Experiments  with  Hydrogen. 

Experiment  a.  —  Inflame  hydrogen  con- 
tained in  a  flask,  and  immediately  pour  in 
some  water.  The  water  does  not  extin- 
guish the  flame,  but  rather  increases  it, 
since  it  rapidly  forces  the  gas  out  of  the 
flask.  The  gas  does  not  burn  in  the  inte- 
rior of  the  vessel,  but  only  on  the  outside, 
where  it  is  surrounded  by  atmospheric  air. 
Experiment  b.  —  Hold  an  empty  tumbler  over  a  fla^k 
of  hydrogen  for  some  minutes,  then  quickly  invert  the 
former,  and  apply  to  it  a  lighted  taper,  when  a  flame 
will  burst  forth  from  the  tumbler  with  a  whizzing  noise. 
The  gas  has  ascended  from  the  flask  into  the  tumbler, 
and  is  consequently  lighter  than  common  air.  In  this  ex- 
periment the  lower  vessel  must  not  be  immediately  ex- 
posed to  the  lighted  taper,  because,  if  all  the  hydrogen  is 
not  displaced,  an  explosion  might  ensue  that  would  break 
the  flask ;  but  if  the  taper  be  applied  after  ten  minutea 


72  METALLOIDS. 

have  elapsed,  the  flask  will  be  found  no  longer  to  con- 
tain any  combustible  gas,  this  having  entirely  escaped. 
Hydrogen  is  the  lightest  of  all  gases ;  14|  measures 
of  it  weigh  only  as  much  as  one  measure  of  atmospheric 
air.  On  account  of  its  levity,  it  is  used  for  filling  balloons. 
Experiment  c.  —  If,  instead  of  the  glass  tube,  a  piece 
of  pipe-stem  be  adapted  to  the  cork  of  the  flask  from 
which  hydrogen  was  evolved,  and  the  gas  then  lighted, 
it  will  bum  like  a  taper.  To  kindle  the  gas,  instead  of 
a  match  or  a  taper,  very  finely  divided  platinum  may  be 
employed.  This  can  be  prepared  in  a  few  minutes  by 
dropping  a  solution  of  platinum  on  blotting-paper,  at- 
taching  it  to  a  wire,  and  igniting  it  over  a 
spirit-lamp,  till  nothing  but  a  gray  coherent 
ash  remains.  The  platinum  is  thus  re- 
duced to  an  extremely  minute  state  of  sub- 
division, and  in  this  state  it  exhibits  the 
remarkable  property  of  igniting  in  hydro- 
gen and  inflaming  it.  It  is  called  spongy 
platinum,  and  is  employed  as  tinder  in  the 
well-known  Dobereiner 's  inflammable  lamp. 
The  apparatus  here  represented  consists  of  a  flask, 
having  the  bottom  broken  off,  and  to  the  neck  of  which 
the  cover  of  the  glass  vessel,  c,  with  the  cock,  e,  is  fastened 
air-tight.  A  piece  of  zinc  is  suspended  in  the  flask  by 
means  of  a  wire.  If  diluted  sulphuric  acid  is  now  poured 
into  the  vessel,  c,  upon  which  the  cover  with  the  flask  at- 
tached is  placed,  then,  the  cock  being  opened,  that  the 
air  contained  in  the  flask  may  be  displaced  by  the  acid 
from  beneath,  hydrogen  is  immediately  evolved  by  the 
contact  of  the  zinc  with  the  acid,  which  hydrogen  must 
be  collected  in  the  flask  by  closing  the  cock,  e,  the  acid 
being  thereby  forced  into  the  exterior  vessel,  until  it  no 
longer  touches. the  zinc.  Upon  opening  the  stop-cock, 
e,  the  gas  issues  from  the  fine  jet,  and  is  directed  against 


HYDROGEN.  73 

the  spongy  platinum,  /.  As  the  gas  es- 
capes, the  sulphuric  acid  passes  again 
into  the  interior  vessel,  and  generates 
fresh  hydrogen  upon  reaching  the  zinc. 
Spongy  platinum  possesses,  in  a  high 
degree,  the  power  of  absorbing  oxygen 
and  condensing  it  within  its  pores ;  if 
hydrogen  be  then  presented  to  it,  these 
two  gases  will  be  brought  into  such  in- 
timate contact,  by  the  powerful  force 
of  attraction,  that  they  will  chemically 
combine  to  form  water,  and  the  heat  thus  liberated  is 
sufficient  to  ignite  the  platinum  tinder,  and  to  inflame 
the  gas,  which  subsequently  issues  from  the  jet.  Many 
aeriform  bodies,  which  do  not  freely  unite  with  each 
other,  can  be  forced  to  combine  by  means  of  spongy 
platinum. 

86.  Explosive  Gas.  —  The  extraordinary  degree  of 
heat  developed  by  the  chemical  union  of  oxygen  and 
hydrogen  may  be  shown  by  the  following  experiments. 
Insert  into  the  opening  of  a  large  pig's  bladder,*  which 
has  been  softened  by  soaking  in  water,  the  broken-off 
neck  of  a  flask,  and  bind  it  firmly  round  with  a  string. 
Then  select  two  perforated  corks,  fitting  this  neck.  One 
cork  is  connected  with  a  bent  glass  tube,  conducting 
the  oxygen  from  the  apparatus  in  which  it  is  evolved 
(§  59)  into  the  bladder,  which  soon  becomes  filled  with  it. 
When  this  operation  is  finished,  replace  the  first  cork 
by  the  second,  having  a  glass  tube  adapted  to  it  only  a 
few  inches  long  and  drawn  out  to  a  point  at  its  outer 
end,  and  provided  with  a  wax  stopple  pressed  upon  the 
opening.  A  glass  tube  may  be  formed  into  a  point  by 
heating  it  in  the  flame  of  a  spirit-lamp,  constantly  turn- 
ing it  round  at  the  same  time,  till  it  becomes  so  soft 
7 


74  METALLOIDS. 

Fig.  4c.  at  the  desired  place,  as  to  be  easily  drawn  out 
Break  it  at  the  slender  part,  and  hold  it  in  the 
flame  for  some  moments,  until  the  sharp  edges  are 
rounded  off  by  incipient  melting.  It  would  be 
more  convenient,  though  somewhat  more  expen- 
sive, to  substitute  for  the  above  contrivance  a  jet 
provided  with  a  small  brass  stop-cock. 
The  bladder  thus  arranged  and  filled  with  oxygen  is 
now  placed  on  blocks,  at  such  a  height  that  the  point  of 
the  glass  tube  shall  be  on  a  level  with  the  hydrogen 
flame,  produced  as  explained  in  a  former  experiment. 
Press  upon  the  bladder  with  the  hand,  and  the  oxygen 
will  escape,  blowing  into  the  hydrogen  flame,  which 
then  takes  a  horizontal  direction.  This  flame  has  but 
little  brilliancy,  less  than  the  hydrogen  flame  alone,  not- 
withstanding which  it  affords  the  greatest  heat  yet 
known.  Hold  in  it  a  platinum  wire,  a  metal  which  has 
never  yet  been  melted  in  the  hottest  furnace,  and  it  will 
melt  like  wax ;  hold  in  it  a  piece  of  chalk  scraped  to  a 
fine  point,  and  it  will  emit  light  (sidereal  light)  of  the 

most  dazzling  splendor. 

Fig.  41. 

A  watch-spring  or  a 
fine  iron  wire  burns 
in  it,  throwing  out 
sparks  as  in  oxygen. 
(§68.)  But  what  is  the 
cause  of  this  powerful 
heat?  It  is  the  result 
of  the  energetic  chem- 
ical combination  of  two 
substances  with  each 

other.     Every  chemical  combination  or  decomposition  is 

attended  with  liberation  of  heat. 

Exact  experiments  have  shown  that  two  measures  of 


HYDROGEN.  7t> 

hydrogen  unite  with  one  measure  of  oxygen,  conse- 
quently in  just  the  same  quantities  as  obtained  in  the 
decomposition  of  water  by  galvanism.  (§  55.)  The  re- 
sult of  the  combination  is  water.  But  two  measures  of 
hydrogen  and  one  of  oxygen  do  not  yield  three  meas- 
ures of  vapor;  they  afford  two  measures  only.  Thus 
the  two  gases  condense  one  third  by  chemical  union. 
If  both  the  hydrogen  and  oxygen  were  suddenly  mixed 
together  and  then  ignited,  the  whole  mass  would  com 
bine  together  at  once,  producing  a  most  violent  report, 
and  bursting  the  vessel  to  pieces.  Such  a  gaseous  mix- 
ture is  called,  for  this  reason,  explosive  gas.  No  dan- 
ger is  to  be  apprehended  from  the  apparatus  described,  as 
the  explosive  gas  is  formed  at  the  point  where  the  oxygen 
meets  the  hydrogen  flame,  and  only  in  small  quantities 
at  once.  This  apparatus  is  an  oxy-hydrogen  blowpipe 
on  a  small  scale.  Hence  explosive  gas  may  be  regard- 
ed as  chemically  decomposed  water,  and  water  as  chem- 
ically combined  explosive  gas,  or  as  burnt  hydrogen. 
Fig.  42.  87.  Experiment.  —  That  water  is  really 

formed  during  the  combustion  of  oxygen  and 
hydrogen,  or  when  they  chemically  unite,  can 
easily  be  shown  by  inverting  a  flask  over  the 
hydrogen  flame ;  the  glass  soon  becomes 
clouded  over,  because  the  water,  which  at 
this  heat  is  generated  in  the  form  of  steam, 
condenses  in  small  globules  on  the  cold  sides 
of  the  glass.  By  this  method  one  fall  meas- 
ure of  water  has  been  obtained  from  one 
thousand  measures  of  oxygen  and  two 
thousand  measures  of  hydrogen. 

By  the  decomposition  of  water  (analysis), 
and  by  combining  together  its  elements  (synthesis), 
it  is  proved  to  consist,  in  volume,  of  one  measure  of 


76  METALLOIDS. 

oxygen  and  two  measures  of  hydrogen,  yielding  two 
measures  of  vapor ;  in  weight,  of  eight  parts  of  oxygen 
and  one  part  of  hydrogen,  yielding  nine  parts  in  weight 
of  water. 

The  great  difference  between  the  numbers  of  the 
measures  and  those  of  the  weight  depends  on  the  fact, 
that  one  measure  of  hydrogen  weighs  sixteen  times  less 
than  one  of  oxygen.  On  account  of  the  property  pos- 
sessed by  hydrogen  when  combined  with  oxygen  of 
forming  water,  the  name  Hydrogen  (generating  water) 
has  been  given  to  it ;  its  chemical  symbol  is  according- 
ly H. 

88.  The  chemical  symbols,  which,  as  previously  stated, 
are  derived  from  the  initials  of  the  Latin  names  of  the 
elements,  present  not  only  a  very  convenient  and  simple 
mode  of  designating  the  elements,  but  they  represent 
also  their  atomic  weights,  which  are  given  at  the  head 
of  the  different  sections.  Consequently  O  signifies  not 
merely  oxygen,  but  100  parts  in  weight  of  it  (pounds, 
ounces,  grains,  &c.) ;  H,  not  only  hydrogen,  but  also  12^- 
proportions  in  weight  of  it.  When  two  elements  are 
in  combination,  this  is  designated  by  uniting  together 
their  symbols ;  H  O,  for  instance,  is  the  formula  for 
water,  and  this  indicates,  not  only  that  water  consists  of 
hydrogen  and  oxygen,  but  also  that  it  is  composed  of 
12^  parts  in  weight  of  hydrogen  (1  At.  H)  and  100 
parts  of  oxygen  (1  At.  O) ;  or  what  is  the  same  thing, 
of  1  part  of  H  and  8  parts  of  O  in  weight.  In  more 
complex  combinations,  the  different  members  are  sepa- 
rated from  each  other  by  a  comma,  or  the  sign  -)->  as  will 
be  seen  in  the  following  sections.  The  smaller  num- 
bers in  the  formula  placed  below  the  letter  modify  only 
the  symbol  immediately  preceding,  but  the  larger  num 
bers  prefixed  to  the  sign  modify  all  the  symbols  as  fai 


HYDROGEN.  77 

as  the  next  comma  or  -[-  sign.  HJ  signifies  accordingly 
two  atoms  of  hydrogen,  Ho,  three  atoms,  &c. ;  but  2  H  O 
indicates  two  atoms  of  hydrogen  and  two  atoms  ol 
oxygen,  &c.  It  is  earnestly  recommended  to  every  be- 
ginner in  chemistry  to  familiarize  himself  with  this  com- 
prehensive language  of  symbols. 

89.  The  change  which  iron  underwent,  when,  by  the 
aid  of  sulphuric  acid,  it  decomposed  water  and  liberat- 
ed the  hydrogen,  remains  now  to  be  considered. 

Experiment.  —  Pour  the  contents  of  the  flask  of  ex- 
periment 83  into  a  porcelain  dish,  heat  them  to  boiling, 
and  filter  them.  A  black  residue  will  remain  on  the 
filter,  which  principally  consists  of  carbon  that  was  con- 
tained in  the  iron;  the  iron  itself  has  been  dissolved, 
and  has  passed  through  the  filter ;  it  is  no  longer  iron 
as  such,  but  has  been  converted  into  a  salt  of  iron, 
which,  on  the  cooling  of  the  solution,  is  deposited  in 
green,  transparent  crystals.  The  formation  of  it  is  ex- 
plained in  the  following  diagram  :  — 

Water  =  oxygen  and  hydrogen 

Iron I  =  oxide  of  iron 

Sulphuric  acid /  =  salt  of  iron. 

This  salt  is  accordingly  called  sulphate  of  iron,  com- 
monly known  as  green  vitriol.  Iron  and  sulphuric  acid 
cannot  combine  directly  with  each  other,  for  it  is  a  rule 
in  inorganic  chemistry,  with  but  few  exceptions,  that 
simple  bodies  unite  only  ivith  simple  bodies,  and  com- 
pound only  with  compound  bodies;  however,  this  com- 
bination can  take  place  when  the  iron  is  oxidized,  and 
thus  converted  into  a  compound  body.  The  water 
contains  the  oxygen  requisite  for  this  purpose,  but  the 
iron  has  not  power  enough  to  extricate  it  without  the 
assistance  of  the  sulphuric  acid,  which,  having  a  strong 
7* 


78 


METALLOIDS. 


affinity  for  a  base,  cooperates  with  it  and  enables  it  to 
overpower  the  water,  and  a  base  is  formed  (protoxide 
of  iron)  which  immediately  unites  with  the  sulphuric 
acid.  The  liberated  hydrogen  escapes  as  gas.  This 
sort  of  affinity  is  called  disposing  affinity. 

Zinc  is  frequently  used  instead  of  iron  in  the  prep- 
aration of  hydrogen. 


AIR. 

90.  The  earth  is  surrounded  by  air,  as  by  a  mantle  : 
it  is  called  the  atmosphere,  and  is  supposed  to  extend 
about  forty-five  miles  above  the  solid  earth.  The  air  pos- 
sesses no  color,  and  is  transparent;  hence  it  is  invisible, 
and  its  particles  are  so  easily  displaced  that  it  cannot 
be  grasped  by  the  hand.  But  it  is  rendered  obvious 
that  the  air  is  material,  and  fills  every  space 
commonly  called  empty,  by  wrapping  moist- 
ened paper  round  a  funnel,  so  that  it  may  fit 
exactly  into  the  mouth  of  a  flask  ;  if  the  fun- 
nel be  now  filled  with  water,  the  fluid  will 
not  run  into  the  flask,  as  the  air  contained  in 
the  latter  will  not  let  it  enter  ;  but  if  the  fun- 
nel be  raised  a  little,  the  air  escapes,  and  the 
water  immediately  rushes  into  the  flask.  We 
learn  also  by  the  balance  that  a  flask  con- 
taining atmospheric  air  weighs  more  than  it  does  when 
the  air  has  been  exhausted  from  it.  But  air  is  so  light 
that  800  measures  of  it  weigh  only  as  much  as  one 
measure  of  water,  yet  the  atmosphere  presses  with 
great  weight  on  the  earth  and  upon  every  thing  there- 
on. But  this  pressure  is  only  noticed  when  the  air  is 
removed  from  a  place,  thus  leaving  it  without  counter- 
pressure. 


AIR. 


79 


Fig.  44. 


91.  Pressure  of  the   Atmosphere.  —  Experiment.  — 
Wrap  some  tow  round  one  end  of  a  stick,  and  grease  it 
with  tallow,  thus  forming  a  plug,  which  must  be  fitted 
tightly  into  a  strong  test-tube.     Boil  some  water  in  the 
test-tube,  and  when  the  air  has  been  expelled  by  the 
steam,   causing   a  vacuum,    insert   the  plug ;    as    the 
water  cools,  the  plug  will  be  pressed  down  upon  the 
surface  of  the  water ;  by  heating,  it  is  again  forced  up 
by  the  steam   thus   generated,   and  by  immersing  in 

cold  water  it  is  again  forced* down. 
In  consequence  of  the  cooling  and 
condensation  of  the  steam  a  vacu- 
um is  formed,  and  therefore  the 
counter-pressure  against  the  weight 
of  the  exterior  air  is  removed ;  the 
pressure  of  the  latter,  accordingly, 
forces  down  the  plug.  On  this 
principle,  the  piston  is  forced  up 
and  down  in  the  cylinder  of  many 
steam-engines. 

92.  This  pressure  often  causes  the  rising  and  falling 
of  liquids  in  tubes. 

Experiment. — If  water  is  boiled  as  was  directed  at  §36 

Fig.  45. 


80 


METALLOIDS. 


Fig.  4§. 


by  means  of  steam,  and  during  the  boiling  the  lamp 
is  removed,  then  the  pressure  of  the  air  acting  on  the 
surface  of  the  water  in  the  beaker-glass  will  very  soon 
force  the  water  contained  in  it  through  the  tube  back 
into  the  flask,  which  in  a  short  time  becomes  quite 
filled  with  water.  The  counter-pressure  of  the  steam 
must  naturally  decrease  as  it  cools  and  condenses.  As 
long  as  the  lamp  is  under  the  flask,  the  pressure  of  the 
steam  is  stronger  than  that  of  the  air,  and 
the  steam,  being  continually  generated, 
forces  the  air  previously  contained  in  the 
flask  into  the  water  of  the  beaker-glass. 
This  reflux  of  liquids  is  particularly  to  be 
feared,  when  such  kinds  of  gases  are  con- 
ducted into  water  as  are  absorbed  by  it  read- 
ily, and  in  large  quantities.  This  is  pre- 
vented by  passing  through  the  cork  a  second 
glass  tube  open  at  both  ends,  and  letting  it 
reach  nearly  to  the  bottom  of  the  flask,  by 
which  tube  air  can  penetrate  into  the  flask  as  the  pres- 
sure of  steam  diminishes.  This  contrivance  is  called  a 
safety-tube. 

93.  Barometer.  —  It  has  been  proved  by  exact  calcu- 
lation that  the  atmosphere 
presses  upon  the  earth  with 
a  force  equal  to  that  of  a 
layer  of  quicksilver  30  inch- 
es deep,  or  a  layer  of  water 
13  y  times  deeper  (34  feet), 
water  being  13  J  times  light- 
er than  quicksilver.  The 
Surf  ace  of  the  earth.  instrument  by  which  the 

amount      of     atmospheric 
pressure  can  be   determined  is   called   the   barometer 


Fig.  47. 


AIR. 


81 


Fill  a  glass  tube>_32  inches  in  length,  one  end  of  which 
is  closed,  with  quicksilver ;  closp  it  with  the  finger,  and 
invert  it  into  a  vessel  of  quicksilver ;  on  removing  the 
finger,  the  mercury  will  not  run  out,  but  will  fall  some 
Fig.  48.  inches,  perhaps  to  s  (Fig.  48).  The  height 

of  the  quicksilver,  from  a  b  to  s,  amounts 
to  about  30  inches.     The  quicksilver  does 
not  fall  lower,  on  account  of  the  external 
pressure  of  the  atmosphere,  which  is  ex- 
erted on  the  quicksilver  at  a  b,  and  not 
at  5,  since  this  end  is  closed.     The  col- 
umn of  quicksilver  in  the  tube  ma}  be 
regarded  as  the  counterpoise  to  the  at- 
mospheric pressure,  and  it  is  hence  con- 
cluded that  the  latter  exerts  just  as  much 
pressure  upon  the  earth  as  a  column  of 
/      quicksilver  30  inches  high.     If  the  tube 
be  opened  at  the  top,  the  pressure  of  the 
air  on  both  extremities  being  then  made 
equal,  the  quicksilver  will  flow  from  the  tube.     The 
space  above  the  quicksilver,  at  s,  is  a  vacuum,  and  is 
Fig.  49.  called   the   Torricellian  vacuum,   from   the 

name  of  the  inventor.  In  common  barom- 
eters the  tube  is  curved  at  the  bottom,  and 
provided  with  a  bulb.  This  bulb  is  open  at 
the  top,  and  supplies  the  place  of  the  vessel 
filled  with  quicksilver  in  the  preceding  fig- 
ure. Here  also  the  pressure  is  only  exerted 
at  one  extremity,  for  the  atmosphere  can 
only  press  on  the  mercury  contained  in 
the  bulb.  The  height  from  o  (Fig.  49)  to 
the  top  of  the  quicksilver  amounts  to  about 
30  inches, 
tf  weights  be  placed  on  one  pan  pf  a  balance,  the 


82  METALI  DIDS. 

opposite  one  will  rise,  but  on  their  removal  it  will  sink, 
The  same  thing  happens  with  the  barometer.  Any  in- 
crease in  the  weight  or  density  of  the  air  presses  the 
quicksilver  up,  and  the  barometer  rises ;  but  any  di- 
minution of  weight  will  make  it  fall.  The  height  of 
the  quicksilver  may  be  read  off  by  affixing  to  the  upper 
part  of  the  tube  a  scale  divided  into  inches  and  tenths 
of  an  inch.  The  mean  state  of  the  barometer  is  at 
30  inches,  and  31  is  called  a  very  high,  and  29  a  very 
low,  state  of  the  barometer.  In  this  part  of  the  coun- 
try, as  a  general  rule,  the  north  and  west  winds  cause 
the  barometer  to  rise,  and  the  south  and  east  winds 
cause  it  to  fall.  The  former  winds,  blowing  chiefly 
from  the  land,  are  cooler,  and  at  the  same  time  drier, 
than  the  latter,  which  pass  over  the  ocean,  there  be- 
coming saturated  with  moisture ;  the  former  likewise 
come  from  colder  into  warmer,  while  the  latter,  on  the 
contrary,  proceed  from  warmer  into  colder  regions  ;  by 
which  the  capacity  of  saturation  for  vapor  is  increased 
in  one  case  and  diminished  in  the  other.  Hence  it  is 
very  natural  that,  when  north  and  west  winds  prevail,  it 
should  rain  less  frequently  than  during  south  and  east 
winds ;  and  that  the  former  winds  are  dry,  while  the 
latter  are  damp.  This  is  perhaps  the  principal  reason 
why  barometers  are  regarded  as  weather  prophets. 

Why  water  does  not  flow  from  a  jar  inverted  over 
the  pneumatic  trough,  why  it  continues  to  flow  through 
a  syphon  after  the  air  has  been  exhausted,  why  liquids 
will  not  run  into  a  vessel  when  the  air  is  confined,  or 
why  water  will  only  rise  to  the  height  of  34  feet  in  a 
suction  pump,  are  questions  that  scarcely  require  fur- 
ther explanation. 

94.  If  the  pressure  or  tension  of  a  confined  quantity 
of  air  be  increased,  by  compressing  it  either  directly  or 


AIR. 


83 


Fig.  50. 


by  the  addition  of  more  air,  it  can  be  forced  to  stream 
out  from  a  small  opening  with  great  rapidity,  as  is 
shown  on  a  small  scale  in  the  common  bellows,  and  on 
a  larger  scale  in  the  blacksmith's  bellows.  Should  there 
be  water  before  this  opening,  the  air  will  press  it  out  in 
a  jet  3r  stream. 

Experiment.  —  Take  a  piece  of  a  fine  glass  tube, 
drawn  out  to  a  point,  and  adapt  it, 
by  means  of  a  perforated  cork,  to  a 
bottle.  Fill  the  bottle  half  full  of 
water,  and  blow  into  it  through  the 
point  of  the  tube ;  when  the  blow- 
ing ceases,  the  air  will  escape  in  a 
stream.  But  if  the  bottle  be  in- 
verted as  soon  as  the  air  is  blown 
in,  then  the  water  will  be  spurted 
out  by  the  compressed  air  above 
Such  an  apparatus  (the  Spritz  or 
washing-bottle)  is  frequently  em- 
ployed for  washing  residues  or  precipitates  remain- 
ing on  filters,  in  order  to  free  them  from  soluble  mat- 
ter. There  is  a  similar  contrivance  connected  with 
the  common  fire-engine,  called  the  wind-hose,  and 
employed  for  throwing  an  uninterrupted  stream  of 
water. 

95.  The  pressure  of  the  atmosphere  exerts  great  in- 
fluence on  the  boiling  of  water,  and  of  other  liquids.  If 
water  is  brought  to  boiling  when  the  quicksilver  in  the 
barometer  is  very  low  (in  foul  weather),  brisk  ebullition 
will  take  place  at  about  99°  C. ;  when  the  quicksilver  is 
is  very  high  (in  clear  weather)  boiling  will  not  occur 
under  101°  C. 

Experiment.  —  Heat  a  flask  half  filled  with  water 
till  the  water  boils  briskly;  then  remove  it  from  the 


84  METALLOIDS. 

Fig.  5i.  nre    and   quickly  cork   it ;    the   boil- 

ing immediately  ceases,  but  will 
commence  again  if  cold  water  be 
poured  over  the  upper  part  of  the 
flask.  In  this  manner  it  can  be  made 
to  bubble  or  boil,  even  though  it  be 
only  lukewarm.  There  is  no  air  in  the 
flask,  it  having  been  expelled  by  the 
steam,  and  it  could  not  reenter  it,  on  the  cooling  and 
condensation  of  the  steam,  on  account  of  its  having 
been  closed.  Consequently  there  is  no  pressure  of  air 
on  the  water,  and  it  will  boil  even  at  a  temperature  of 
20°  C.  The  boiling  ceased  on  account  of  the  pressure 
of  the  steam  upon  the  water ;  but  the  steam  being  con- 
densed by  the  cold  water,  the  pressure  was  so  much 
diminished,  that  a  portion  of  water  again  became  aeri- 
form with  a  boiling  motion.  In  many  manufactories, 
an  appropriate  apparatus  has  been  contrived  for  boiling 
and  evaporating  in  a  vacuum,  as,  for  instance,  in  sugar- 
houses. 

The  air  is  densest  at  the  level  of  the  sea,  and  thinner 
in  proportion  to  its  distance  from  the  earth,  as  there  is 
less  air  above  it.  Hence  the  mercury  will  stand  lower, 
and  water  boil  more  easily,  on  the  top  of  a  mountain 
than  in  the  valley  below.  On  the  top  of  Mont  Blanc 
quicksilver  rises  only  to  the  height  of  16  inches  in  the 
barometer,  and  water  boils  at  84°  C.  Hence  the  barom- 
eter and  the  boiling  point  of  water  may  be  employed 
for  calculating  the  heights  of  mountains. 

96.  As  water  boils  more  easily  under  diminished 
pressure,  so  it  boils  with  more  difficulty  when  the  pres- 
sure is  increased.  An  increase  of  pressure  can  be  pro- 
duced, not  only  by  the  air,  but  by  the  steam  of  the  wa- 
ter itself,  if  new  steam  be  constantly  generated,  while 


AIR. 


85 


the  escape  of  that  already  formed  is  prevented.  This  is 
best  done  by  heating  water  confined  in  a  strong  and 
firmly  closed  vessel.  For  this  purpose  a  Papin's  Di- 
gester may  be  used,  in  which  water  may  be  heated  to 
the  temperature  of  200°  C.,  and  indeed  still  higher, 
whilst  in  open  vessels  it  cannot  be  heated  above  100°  C. 
If  the  amount  of  steam  in  it  is  twice  as  much  as  in  an 
uncovered  vessel,  the  pressure  is  said  to  amount  to  two 
atmospheres ;  if  there  is  3,  4,  5,  10,  20  times  the  quan- 
tity, there  is  said  to  be  a  pressure  of  3,  4,  5,  10,  2C  at- 
mospheres. Vessels  of  this  kind  are  often  employed  to 
effect  a  complete  penetration  of  the  water  into  solid  and 
hard  substances.  Thus,  for  example,  water  at  100°  C. 
dissolves  the  gelatinous  matter  only  on  the  surface  ot 
the  bones,  whilst  water  at  a  temperature  ranging  from 
110°  to  120°  entirely  penetrates  the  bones,  and  extracts 
the  gelatine  also  from  the  interior  of  them. 

97.  Air  and  Heat.  —  Heat  expands  the  air  in  quite  the 
same  way  as  it  does  solid  and  liquid  bodies,  but  to  a 
much  greater  extent. 

Experiment.  —  Dip  a  glass  tube,  provided  with  a 
bulb,  into  water,  and  heat  the  bulb 
gently ;  a  part  of  the  air  is  expelled, 
and  escapes  in  bubbles  through  the 
water;  consequently,  there  is  not 
room  enough  in  the  bulb  for  the 
heated  air ;  but  it  requires  a  larger 
space  than  it  did  in  its  cold  condi- 
tion. It  follows  from  this,  also, 
that  the  warm  air  is  lighter  than 
cold.  If  the  lamp  be  removed, 
the  air  remaining  in  the  bulb  will 
contract  on  cooling,  and  water  will 
8 


Fig.  52. 


86 


METALLOIDS. 


be  pressed  up  into  the  bulb,  replacing  the  air  which  has 
been  expelled. 

98.  Current  of  Air.  —  A  great  many  phenomena  of 
daily  occurrence  may  be  explained  by  the  difference  in 
levity  between  warm  and  cold  air.  When  a  fire  is 
kindled  in  a  stove  for  the  heating  of  an  apartment,  the 
air  immediately  in  contact  with  the  stove  is  first  heated, 
becomes  lighter,  and  ascends ;  colder  air  rushes  in  to 
supply  its  place,  and  this  is  likewise  heated  and  as- 
cends ;  consequently,  a  constant  circulation  of  air  is 
kept  up.  By  a  similar  circulation,  the  whole  atmos- 
phere of  the  earth  is  kept  in  continual  motion.  At  the 
equator  the  strongly  heated  air  ascends  and  moves  in  the 
upper  regions  of  the  atmosphere  towards  the  poles,  while 
in  the  lower  regions  the  current  of  cold  air  flows  from 
the  arctic  zone  towards  the  equator,  in  order  here  to  re- 
store again  the  equilibrium,  disturbed  every  moment  by 
the  ascent  of  the  warm  air.  These  regular  currents  of 
air,  the  direction  of  which  is  somewhat  diverted  by  the 
revolution  of  the  earth  on  its  axis,  are  called  trade-winds. 

In  every  heated  apart- 
ment, a  difference  between 
the  heat  of  the  air  near  the 
ceiling  and  that  near  the 
floor  is  very  perceptible. 
If  a  door  or  window  in 
such  a  room  be  opened,  a 
current  of  air  is  produced, 
the  direction  of  which  may 
easily  be  perceived  by 
holding  a  lighted  candle 
in  the  opening ;  the.  flame, 
when  held  above,  at  c 
(Fig.  53),  is  blown  from 


Fig  53. 


AIR.  87 

the  room ;  when  placed  below,  at  0,  it  is  blown  into  it; 
consequently,  the  light  warm  air  above  rushes  out  of  the 
room,  and  is  replaced  by  heavier  and  colder  air  from  be- 
low. A  draught  of  air  is  also  noticed  in  passing  from 
the  sunshine  into  the  shade ;  where  the  sun  shines,  the 
warmer  air  ascends,  and  the  colder  air  from  the  shade 
supplies  its  place.  For  the  same  reason,  a  current  of 
air  is  produced  wherever  a  fire  is  burning,  in  every 
stove,  and  round  every  lamp. 

The  air-balloons,  first  constructed  by  Montgolfier, 
strikingly  show  how  buoyant  %air  may  be  rendered 
by  heat;  these  are  caused  to  ascend  merely  by  fill- 
ing them  with  air,  kept  continually  hot  by  a  fire  be- 
neath. 

99.  Gases.  —  Formerly,  atmospheric  air  only  was 
known,  but  chemistry  has  shown  that  there  are  various 
kinds  of  air,  light  and  heavy,  poisonous  and  innocent; 
some  which  are  combustible,  others  not  so,  but  which 
will  support  combustion,  and  others  which  extinguish  it, 
It  has  also  been  shown  that  some  sorts  of  air  are  conceal- 
ed or  chemically  bound  in  many  solid  and  liquid  bodies, 
in  which,  from  their  external  appearance,  the  presence 
of  gases  would  never  have  been  suspected  ;  as,  for  in- 
stance, oxygen  in  oxide  of  mercury,  and  oxygen  and 
hydrogen  in  water.  These  kinds  of  air  are  commonly 
called  gases.  The  aeriform  state  is  their  natural  con- 
dition, and  they  only  assume  the  solid  or  liquid  state  on 
compulsion.  Their  densities,  like  solids  and  liquids 
(§23),  are  likewise  expressed  in  numbers;  but  it  must 
be  remembered  that  in  this  case  atmospheric  air,  and 
not  water,  is  assumed  as  unity. 

Vapor.  —  Many  other  bodies  become  aeriform  on 
being  heated,  some  quite  easily,  as  alcohol  and  water ; 
others  with  more  difficulty,  as  sulphur  and  mercury; 


00  METALLOIDS. 

but  on  being  cooled  they  lose  their  gaseous  form,  and 
assume  again  the  liquid  or  solid  state.  Such  species  ot 
air  are  called  vapor  or  steam;  they  become  gaseous  only 
upon  compulsion,  their  natural  state  is  liquid  or  solid. 

Composition  of  Air. 

100.  The  last  question  concerning  air  is,  What  are 
its  component  parts  ?  for  that  it  is  not  a  simple  sub- 
stance, not  an  element,  has  already  been  stated. 

Experiment.  —  Fasten  a  piece  of  tinder  to  a  wire,  drop 
some  alcohol  upon  it,  and  hold  the  wire  in  a  vessel  con- 
taining water,  so  that  the  tinder  may  be  some  inches 
above  the  water.  Then  kindle  the 
spirit,  and  immediately  place  an 
empty  flask  over  it,  so  that  the  mouth 
of  it  may  dip  into  the  water;  the 
flame  will  soon  cease  burning,  and 
some  of  the  water  will  rise  into  the 
flask,  in  proportion  to  the  amount  oi 
air  disappearing  during  the  combus- 
tion. The  consumed  air  was  oxygen, 
which  united  with  the  constituents 
of  the  alcohol.  Close  the  flask  tightly  with  the  finger, 
shake  it  briskly,  and  again  open  it  below  the  water, 
when  a  little  more  water  will  enter.  The  air  which  is 
in  the  flask  is  called  nitrogen;  it  is  sometimes  called 
azote  (a  privative,  and  M,  life),  from  its  inability  to 
support  respiration.  It  forms  the  chief  element  of  at- 
mospheric air;  this  consisting  of  four  measures  of 
nitrogen,  and  only  one  of  oxygen. 


NITROGEN. 

NITROGEN  OR  AZOTE  (N). 
At.  Wt.  =  175.  —  Sp.  Gr.  =  0.97. 

101.  Nitrogen  gas,  the  preparation  of  which  has  just 
been  given,  is  erroneously  called  azote,  as  we  are  con- 
tinually breathing  it  without  perceiving  any  injurious 
effects  trim  it ;  it  stops  respiration  only  when  it  con- 
tains no  oxygen,  and  because  it  contains  none.     The 
human  body  is  so  constructed,  that  it  will  not  thrive  on 
substances  intended  as  nourishment  if  they  are  present- 
ed to  it  in  their  purest  form.     Strong  alcohol  acts  as  a 
poison,  but  when  diluted  with  four  or  five    times    its 
quantity  of  water,  as  in  wine,  it  is  invigorating.     Even 
the  respiration  of  oxygen  would  soon  destroy  life,  were 
it  not  diluted  with  four  times  its  measure  of  nitrogen, 
as  in  atmospheric  air.  ^ 

Nitrogen  has  neither  color,  smell,  nor  taste,  and  in  a 
chemical  point  of  view  it  must  be  regarded  as  a  very 
inert  or  indifferent  body,  since  it  does  not  combine  di- 
rectly with  any  other  substance.  If  we  would  combine 
it  with  another  body,  we  must  adopt  a  circuitous  meth- 
od. It  is  very  widely  diffused  in  nature,  particularly  in 
the  organic  kingdom,  for  we  find  it  in  all  plants  and 
animals.  It  is  also  contained  in  saltpetre  or  nitre, 
whence  its  name  nitrogen  (generator  of  nitre) ;  its  sym- 
bol is  N. 

102.  Besides  oxygen  and  nitrogen,  air  contains  vapor 
and  carbonic  acid.  -  The  presence  of  the  former  is  ren- 
dered  obvious    by    the   fall  of  rain,  snow,  dew,  &c. ; 
and  that  of  carbonic  acid  can  easily  be  determined  by 
letting  lime-water  remain  exposed  to  the  air,  as  in  §  46, 
or  by  shaking  it  in  a  flask  containing  air.     Lime  has  an 
affinity  for  carbonic  acid,  and  forms  with  it  an  insoluble 
salt  (carbonate  of  lime,   or   chalk).     This  occasions  a 

8* 


90  METALLOIDS. 

cloudiness  in  the  liquid ;  it  is  the  affirmative  answer  to 
the  question  put  by  the  lime-water  to  the  air.  If  you 
ask,  What  is  the  source  of  this  carbonic  acid  ?  the  re- 
ly is,  It  is  formed  wherever  substances  are  burning, 
wherever  men  and  animals  are  breathing,  and  wherever 
decay  and  putrefaction  are  taking  place. 

In  100  measures  of  atmospheric  air  are  contained,  — 
79  measures  of  nitrogen,  or  N. 

21         «  «    oxygen,  "    O. 

_i0-_i_     «  «    carbonic  acid,      "    CO,, 

and  variable  quantities  of  water,   "    H  O. 

In  crowded  rooms,  and  other  confined  places,  the  air 
becomes  deteriorated  ;  that  is,  poorer  in  oxygen  and 
richer  in  carbonic  acid. 

That  the  air  also  contains  other  foreign  ingredients  is 
not  strange,  since  it  is  the  constant  receptacle  of  vol- 
atile substances  and  dust.  The  air  coming  from  the 
Spice  Islands,  even  at  the  distance  of  eight  or  ten  miles, 
is  impregnated  with  the  odor  of  cinnamon  and  cloves. 
The  dust  contained  in  the  air  can  be  discerned  in  the 
sun-beam,  &c.  These  ingredients  are  usually  so  small, 
that  they  can  be  determined  neither  by  weight  nor 
by  measure. 

COAL   AND   FIRE. 
CARBON  (C). 
At.  Wt.  =  75. 

103.  If  a  piece  of  wood  be  placed  on  the  hot  hearth 
of  a  stove,  it  becomes  brown,  and  finally  black,  —  it  is 
charred.  If  water  be  poured  over  a  burning  chip,  the 
latter  is  extinguished,  —  it  is  likewise  charred.  A  piece 
of  linen,  when  inflamed  and  immediately  smothered, 
becomes  tinder.  Tinder  is  charred  linen.  In  the  first 


CARBON.  9 1 

case,  the  heat  was  not  sufficiently  strong  entirely  to 
consume  the  wood;  in  the  second,  the  complete  burn- 
ing was  prevented  by  quenching,  and  in  the  third  by 
the  exclusion  of  air.  All  animal  and  vegetable  substan- 
ces, if  only  partially  burnt,  are  converted  into  coal.  As 
coal,  on  exclusion  of  the  air,  cannot  be  melted,  even  in 
the  strongest  heat,  so  the  exterior  of  it  is  very  different, 
according  to  the  character  and  structure  of  the  sub- 
stance from  which  it  was  prepared ;  indeed,  this  differ- 
ence often  extends  itself  throughout  the  interior  struc- 
ture, as  in  charcoal,  soot,  coke,  bone-black,  &c.  In  the 
charring  of  organic  bodies  the  coal  is  not  generated,  but 
it  previously  existed  in  them,  though  in  chemical  combi- 
nation with  other  substances,  which  are  principally  driv- 
en off  by  heat,  as  is  obviously  the  case  from  the  fact 
that  the  charred  body  weighs  much  less  than  the  orig- 
inal substance.  All  animals  and  plants  consist,  there- 
fore, partly  of  coal ;  or,  in  chemical  language,  of  Car- 
bon =  C. 

Carbon  also  exists  in  the  mineral  kingdom.  It  forms 
the  principal  element  of  pit  coal,  brown  coal,  &c.,  which 
have  all  been  formed  from  the  vegetation  of  an  earlier 
period.  It  is  found  almost  pure  in  the  diamond  and 
in  the  graphite,  and,  combined  with  oxygen,  is  con- 
tained in  limestone,  marble,  chalk, 
_  and  various  other  minerals. 

104.  Charcoal  (C  containing  a 
little  ashes.) 

Experiment.  —  Gradually  intro- 
duce a  burning  splinter  of  wood 
into  a  test-tube.  The  part  out- 
side of  the  tube  only  will  burn 
with  a  flame,  while  that  within 
merely  chars,  because  the  air  is 


»^  METALLOIDS. 

excluded.  On  the  same  principle,  charcoal  is  prepared 
on  a  large  scale.  Piles  of  wood  (charcoal  kilns)  are 
erected,  which  are  covered  with  turf  and  moistened 
earth,  and  the  wood  is  then  kindled.  This  would  be 
extinguished,  however,  for  want  of  air,  if  holes  were 
not  made,  by  wooden  pokers,  at  different  parts  of  the 
kiln,  through  which  fresh  air  may  be  admitted,  and  the 
burnt  air  may  escape.  Only  so  much  air  should  be  ad- 
mitted as  is  necessary  for  carbonizing  or  half-burning  the 
wood.  When  this  has  been  accomplished  in  the  neigh- 
bourhood of  the  holes,  they  must  be  closed,  and  new 
ones  made  at  other  points.  At  last  all  the  openings  are 
carefully  stopped,  that  the  fire  may  be  suffocated.  When 
cold,  the  wood  will  be  found  thoroughly  burnt  to  black- 
ness and  charred,  the  shape  of  the  knots  and  rings 
being  still  perceptible.  One  pound  of  wood  yields 
about  one  quarter  of  a  pound  of  charcoal. 

105.  Experiments  with  Charcoal. 

Experiment  a.  —  Weigh  a  piece  of  freshly-burnt  cnar- 
coal,  and  let  it  remain  for  a  day  in  a  moist  place ;  it 
will  now  weigh  more  than  before,  owing  to  its  having 
imbibed  air  and  moisture.  If  the  coal  be  now  put  into 
hot  water,  the  air  will  escape  from  the  coal  in  numerous 
bubbles,  being  expelled  by  the  heavier  water,  which  re- 
places the  air  in  the  small  interstices  or  pores  of  the 
coal.  The  snapping  of  such  coals  when  placed  upon 
the  fire  is  hereby  easily  explained  ;  the  gases  and  vapors 
ar ?  expanded  to  such  an  extent  by  the  sudden  heat,  that 
the  coal  is  forced  asunder,  with  a  sort  of  explosion. 
Polished  steel  articles  are  often  packed  up  in  charcoal 
dust,  that  the  air  in  the  interior  of  the  package  may  be 
kept  dry,  thus  protecting  the  steel  from  rusting.  Pulver- 
ized charcoal,  on  account  of  its  absorbing  power,  may 


CARBON.  y<3 

- 

also  be  vised  for  purifying  sick-rooms,  arid  other  apart- 
ments filled  with  deleterious  vapors  and  gases. 

Experiment  b.  —  Grind  freshly-burnt  charcoal  to  a 
coarse  powder,  and  place  it  on  a  filter.  Then  pour  over 
H  some  red  wine,  or  some  water  colored  black  by  a  few 
Fin.  m  drops  of  ink  ;  the  liquid  will  pass  through  the 
filter  nearly  or  quite  colorless,  the  coal  hav- 
ing absorbed  or  retained  the  coloring  matter. 
Sugar-refiners  take  advantage  of  this  property 
of  charcoal  in  bleaching  their  brown  syrups. 
Experiment  c.  —  Foul  stagnant  water  is 
deprived  of  its  bad  taste,  and  is  rendered  clear 
and  colorless,  by  being  filtered  through  char- 
coal. In  some  large  cities,  where  there  is  a 
scarcity  of  potable  water,  it  is  not  unusual  to  filter  it 
through  charcoal.  Grain,  likewise,  which  has  become 
musty,  may  be  rendered  sweet  by  intimately  mixing 
it  with  pulverized  charcoal,  and  allowing  them  to  re- 
main some  weeks  in  contact.  Coal  will  also  retard 
decay  in  vegetable  and  animal  substances  for  a  long 
period,  and  water  remains  pure  for  years  in  vessels 
which  have  been  charred  upon  the  inside ;  potatoes  may 
be  kept  in  cellars  longer,  without  sprouting  or  rotting, 
when  laid  in  with  coal-dust ;  and  meat,  when  packed  in 
it,  passes  more  slowly  into  a  state  of  putrefaction. 
.  Experiment  d.  —  Charcoal  renders  ordinary  brandy 
pleasanter  in  taste  and  smell,  by  absorbing  into  its 
pores  an  acrid  volatile  oil,  fusel  oil,  with  which  some 
crude  brandy  is  contaminated.  Coal  deprives  beer  of 
its  bitterness,  by  absorbing  certain  component  parts  of 
the  hops. 

106  The  cause  of  this  remarkable  power  of  coal  to 
attract  and  retain  within  itself  such  various  substances, 
depends  on  its  spongy,  porous  character.  If  a  plate  of 


94  METALLOIDS. 

glass  be  dipped  into  water  and  immediately  removed, 
some  of  the  water  will  remain  adhering  to  its  surface, 
showing  that  the  water  and  glass  have  an  attraction  for 
each  other.  This  power  is  called  surface-attraction,  or 
adhesion.  This  adhesion  can  be  better  illustrated  by 
dipping  a  glass  tube  with  a  fine  bore  into  water ;  the 
water  rises  in  it,  and  the  rise  in  the  tube  will  increase. 
Fig.  57.  in  proportion  to  the  decrease  of  the  di- 

ameter. Such  tubes  present  a  great  sur- 
face of  glass  to  a  small  amount  of 
liquid,  and  the  sides  are  in  such  close 
proximity,  that  they  aid  each  other  in 
drawing  up  the  water  into  the  tube. 
This  sort  of  adhesion  is  called  capillary 
attraction.  It  is  this  which  causes  oil  to 
rise  in  the  lamp-wick,  the  spreading  of 
water  in  blotting-paper,  and  the  diffusion  of  moisture 
through  sugar  and  plastered  walls.  In  the  same  man- 
ner, all  solid  bodies  which  have  many  pores,  and  conse- 
quently much  surface,  attract  fluids  and  gases.  A  piece 
of  charcoal,  the  size  of  a  walnut,  is  intersected  by 
many  hundreds  of  partitions,  which,  if  they  could  be 
placed  by  the  side  of  each  other,  would  cover  a  space  a 
thousand  times  larger  than  the  piece  of  coal  itself 
covered.  The  force  of  attraction  of  this  large  surface 
is  so  powerful,  that  the  coal  can  absorb  from  80  to  90 
times  more  than  its  own  bulk  of  many  species  of  gas. 
It  is  very  probable  that  these  gases,  by  such  a  com  pres- 
sure into  80  or  90  times  smaller  space  within  the  coal, 
become  fluid  or  solid. 

In  the  case  of  spongy  platinum  (§  85,  c),  a  yet  more 
porous  substance  than  coal,  heat  is  produced,  in  con- 
sequence of  the  absorption  of  oxygen  and  hydrogen 
rendering  the  platinum  red-hot.  Heat,  also,  but  to  a 


CARBON.  9O 

less  extent,  is  developed  in  charcoal  when  it  absorbs 
gases  ;  the  charcoal  may  be  heated  even  to  redness, 
undergoing  spontaneous  combustion,  by  heaping  to- 
gether large  masses  of  it  in  a  pulverized  state,  and 
many  an  unfortunate  accident  has  occurred  from  this 
cause,  especially  in  factories  for  the  manufacture  of 
gunpowder. 

Hydrogen  and  oxygen,  however  long  they  remain  in 
contact,  do  not  enter  into  chemical  union,  but  when  the 
mixture  is  brought  into  contact  with  spongy  platinum 
they  instantly  unite,  forming  water.  This  will  be 
easily  understood,  when  it  is  remembered  that  chemical 
force  acts  only  at  insensible  distances,  and  consequently 
only  when  substances  are  in  the  very  closest  contact- 
In  spongy  platinum,  as  in  other  porous  bodies,  gases 
can  be  condensed  to  the  80th,  and  indeed,  in  the  former 
case,  to  the  800th  part  of  their  volume  ;  they  must  there- 
fore touch  each  other  from  80  to  800  times  more  closely 
than  in  their  natural  condition. 

107.  Not  only  charcoal,  but  the  following  varieties  of 
coal)  have  many  different  applications. 

Soot^  or  lamp-black^  (C  containing  empyreumatic 
matter,)  is  coal  in  a  state  of  minute  division,  which  is 
deposited  from  carbonaceous  gases,  commonly  from  il- 
luminating gas  ;  for  instance,  from  the  flame  of  pit- 
coal,  wood,  oil,  rosin,  &c.,  when  during  the  combustion 
there  is  an  insufficient  supply  of  air.  One  variety  of 
superior  quality  is  called  lamp-black.  (§  116.)  The  soot 
must  be  freed  from  the  empyreumatic  substances,  either 
by  igniting  it  thoroughly  in  a  well-closed  vessel,  or  by 
treating  it  with  strong  alcohol.  Soot  is  well  known  as 
a  most  important  black  coloring  substance  (Indian 
ink,  printing-ink). 

Coke,  or  charred   pit-coal,    (C  generally   containing 


96  METALLOIDS. 

considerable  quantities  of  ashes,)  has  a  gray  color,  is 
more  or  less  porous,  is  very  hard,  and  has  a  metallic 
lustre ;  it  burns  without  forming  soot,  and  gives  out  an 
intense  heat;  hence  it  is  an  excellent  fuel,  and  es- 
pecially adapted  for  the  smelting  of  iron,  and  for  the 
heating  of  locomotive  boilers.  Coke  is  obtained  as  a 
secondary  product  in  the  preparation  of  illuminating 
gas  from  pit-coal.  (§  118.) 

Bone-black  (C  intimately  mixed  with  bone-ashes, 
and  generally  also  with  some  azotized  substances)  is 
obtained  by  heating  bones  in  close  vessels.  The  coal 
contained  in  it  amounts  only  to  about  one  tenth  part  of 
the  whole,  the  other  nine  tenths  being  bone-ashes  ;  but 
notwithstanding  this,  its  decolorizing  power  is  so  strong, 
that  it  is  preferred  to  all  other  kinds  of  coal  as  a  means 
of  abstracting  color  from  the  syrup  of  brown  sugar,  or 
from  other  dark  liquids. 

Two  sorts  of  carbon  found  in  the  mineral  kingdom, 
viz.  graphite  and  the  diamond,  possess  very  remark- 
able, yet  different,  properties. 

Graphite,  or  plumbago,  (crystallized  black  carbon,)  a 
gray  substance,  having  a  metallic  lustre,  imparts  its 
color  so  readily  to  other  bodies,  that  it  is  used  for  mak- 
ing lead  pencils,  and  for  giving  a  black  polish  to  iron 
articles,  such  as  stoves,  &c. ;  it  is  so  soft  and  lubricating, 
that  it  is  added  to  grease  for  the  purpose  of  preventing 
friction  in  wheels  and  machinery ;  it  is  also  so  nearly  in- 
combustible, that  crucibles  are  made  of  it,  which  endure 
the  strongest  fire  without  burning  (blue-pots). 

Diamond,  (crystallized  colorless  carbon)  is  the  hardest 
of  all  bodies.  In  external  appearance  it  has  not,  indeed, 
the  slightest  resemblance  to  coal,  yet  it  can  be  entirely 
burnt  up  in  oxygen,  and  carbonic  acid  is  the  only  prod- 
uct obtained  from  it,  and  exactly  so  much  is  obtained 


CARBON.  97 

as  would  have  "resulted  from  the  combustion  of  an 
equally  heavy  piece  of  charcoal  or  coke.  In  order  to 
crystallize  a  substance,  it  must  first  be  rendered  fluid, 
which  is  done  either  by  melting  or  dissolving  it.  Coal 
can  neither  be  melted  by  the  strongest  heat,  nor  dis- 
solved in  any  known  liquid.  Should  a  method  ever  be 
discovered  for  rendering  it  liquid,  then  diamonds  could 
certainly  be  artificially  imitated. 

108.  Carbon  shows  very  clearly  how  one  and  the 
same  body  can  have  quite  different  forms  and  different 
properties.  In  charcoal,  soot,  coke,  and  animal  carbon, 
it  is  black  without  any  determined  shape  (amorphous) } 
and  very  combustible ;  in  graphite  it  is  black,  with  a 
crystallized  foliated  structure,  and  is  nearly  incom- 
bustible ;  in  the  diamond  it  is  colorless,  and  is  crystal- 
lized as  a  four-sided  double  pyramid  (octahedron),  and 
is  likewise  almost  incombustible.  Hence  carbon  is  said 
to  be  dimorphous,  having  two  different  crystalline  forms. 
If  a  body  can  assume  more  than  two  crystalline  forms 
it  is  said  to  be  polymorphous,  having  many  forms. 

This  property,  which  many  elements  have,  of  as- 
suming different  forms,  is  also  called  allotropic  (from 
dAAorpoTTos,  different  nature),  and  it  is  designated  by  an- 
nexing Greek  letters  to  the  chemical  symbols.  Accord- 
ingly carbon  occurs  in  the  three  following  allotropic 
states  or  modifications  ;  as  Ca  in  diamond,  C /3  in 
graphite,  and  C  y  in  charcoal. 

The  cause  of  this  difference  depends  upon  the  relative 
position  of  the  particles  or  atoms  constituting  the  body 
towards  each  other.  The  same  fibres  of  cotton,  which, 
after  carding,  are  parallel  to  each  other,  when  matted  to- 
gether without  order,  constitute  paper  or  paste-board  ; 
when  loosely  woven  together,  wadding ;  when  twisted, 
yarn  or  thread,  and  when  they  are  made  to  intersect 
9 


98  METALLOIDS. 

each  other  regularly,  or  in  some  intricate  manner,  cloth 
stockings,  velvet,  &c.  Nature  also  impresses  different 
forms  upon  the  same  substance,  but  in  a  still  more 
varied  and  artistical  manner.  The  adaptation  of  the 
atoms  to  each  other  is  not  rendered  visible  to  us,  even 
by  the  aid  of  the  strongest  microscope ;  but  this  theory 
may  be  regarded  as  correct,  since  it  explains  the  sub 
ject  in  a  simple  and  natural  manner. 

109.  Coal  and  Oxygen. —  Coal  undergoes  no  change 
on  exposure  to  the  air,  or  when  imbedded  in  the  ground 
It  is  not  decomposed  at  common  temperatures,  that  is, 
it  does  not  enter  into  combination  with  the  oxygen  ol 
the  air  or  of  water.  But  this,  as  is  well  known,  takes 
place  very  readily,  when  heated  to  redness.  It  then 
burns  and  disappears,  with  the  exception  of  a  small 
quantity  of  ashes.  The  heat  thus  developed  is  the  re- 
sult of  the  chemical  union  of  the  carbon  with  the 
oxygen  of  the  air.  The  gas  generated  is  called  carbonic 
acid,  which  forms,  with  lime-water,  a  white  precipitate 
(carbonate  of  lime),  as  has  been  stated  previously 
Carbonic  acid  consists  of  one  atom  of  carbon  and  two 
atoms  of  oxygen,  consequently  its  formula  is  =  C  Oa 
It  may  also  be  obtained  as  follows. 

Carbonic  Acid.  —  Experiment.  —  Mix  109  grains  oi 
oxide  of  mercury  with  four  grains  of  charcoal,  and  heal 
them  in  a  test-tube  (§  56).  A  lighted  taper  introduced 
into  the  gas  is  extinguished,  a  sign  that  it  contains 
no  free  oxygen.  If  you  shake  it  with  lime-water,  the 
liquid  becomes  turbid,  and  on  shaking  the  flask  the 
finger  is  sucked  in,  or  rather  it  is  pressed  into  the  neck 
of  the  flask  by  the  atmospheric  air,  a  proof  that  the  gas 
was  absorbed  by  the  lime-water,  and  that  a  vacuum 
was  produced  within  the  vessel.  If  the  oxide  of  tner- 
cury  had  been  heated  by  itself  (  §56 ),  it  would  have 


CARBON, 


Fig.  68.  separated       into 

mercury  and  ox- 
ygen ;  and  this 
also  happens  in 
the  present  ex- 
periment, but  the 
oxygen  does  not 
escape  as  such,  it 
having  previous- 
ly united  with 
part  of  the  coal 
the  gas  evolved 
is  carbonic  acid. 
The  mercury  is 
found,  as  a  metallic  mirror,  at  the  upper  part  of  the 
test-tube.  After  the  experiment  is  finished,  some 
coal  still  remains  in  the  test-tube,  for  only  3  grains 
of  it  have  united  with  the  8  grains  of  oxygen  con- 
tained in  the  oxide  of  mercury ;  consequently,  in  the 
same  proportions  as  in  the  burning  of  charcoal  in  pure 
oxygen.  (§§  63,  70.)  We  see  that  3  grains  of  carbon 
combine  with  as  much  oxygen  as  101  grains  of  mer- 
cury, or  (§  70)  with  as  much  oxygen  as  8  grains  of  sul- 
phur, 6  grains  of  phosphorus,  23  grains  of  sodium,  or 
20  grains  of  iron.  These  numbers  are  called  equiva- 
lents;  they  indicate  that  3  grains  of  carbon  have  the 
same  chemical  value  as  101  grains  of  mercury,  or  as  8 
grains  of  sulphur,  &c.  In  the  same  sense,  when  we 
sec  a  steam-engine  perform,  in  one  day,  the  work  for 
which  four  hor&^c  ?r  twenty-four  men  were  required,  we 
say  that  Llio  power  of  the  steam-engine  is  equivalent 
to  the  power  of  four  horses  or  twenty-four  men.  (§  164). 
110.  Carbonic  Oxide  Gas.  —  When  charcoal,  during 
combustion,  has  a  sufficient  supply  of  air,  then  carbonic 


100  METALLOIDS. 

acid,  or  C  O2,  is  formed ;  but  if  there  is  a  deficiency  01 
air,  then  3  grains  of  charcoal  unite  with  only  half  ag 
much  oxygen,  namely,  with  4  instead  of  8  grains,  and 
there  is  produced  but  half-made  carbonic  acid,  as  it 
were,  which  is  called  carbonic  oxide  gas  =  C  O.  Car- 
bonic oxide  gas  is  extremely  poisonous  when  inhaled, 
and  constitutes  what  the  miners  call  coal-gas.  This 
gas  is  always  formed  when  charcoal  burns  slowly,  for 
example,  in  a  chafing-dish,  because  the  ashes,  accumu- 
lating round  the  coals,  obstruct  the  access  of  air;  and 
it  is  also  formed  when  the  damper  of  a  stove  is  closed, 
before  the  coal  is  burnt  out,  since  in  this  case  the 
draught  of  air,  and  consequently  the  supply  of  sufficient 
oxygen,  is  prevented.  Notwithstanding  repeated  warn- 
ings, accidents  not  seldom  occur  from  the  fumes  of 
burning  charcoal.  Carbonic  oxide  burns,  when  kindled, 
with  a  blue  flame ;  it  takes  up  the  deficiency  of  oxygen 
not  supplied  to  it  by  the  air  while  forming,  and  is  con- 
verted into  carbonic  acid ;  that  is,  it  takes  up  as  much 
again  oxygen,  and  C  O  becomes  C  (X.  The  blue  flame 
which  is  always  perceived  on  feeding  the  fire  with  fresh 
coals,  or  in  large  masses  of  glowing  coals,  is  burning 
carbonic  oxide  gas. 

COMBUSTION. 

111.  Every  combustion  with  which  we  are  familiarly 
acquainted  is  caused  by  a  rapid  chemical  union  of  com 
bustible  bodies  with  the  oxygen  of  the  air,  and  the  pro- 
cess may  be  regarded  as  one  of  oxidation.      The  con- 
sumed or  oxidized  combustible  substances,  that  is,  the 
compound  of  the  fuel  with  oxygen,  are  mostly  aeriform 
We  call  them  smoke,  which  will  not  support  combus 
tion.     It  follows  from  this,  that,  in  order  to  mahitaJ1' 


COMBUSTION. 


lOi 


F\Z  59. 


combustion,  fresh  air  must  be  continually  supplied  to  the 
fire,  and  the  smoke  conducted  off.  This  is  effected  by  a 
current  of  air. 

Experiment.  —  Place  the  glass  cylinder  of  a  lamp 
over  a  lighted  candle,  which  will 
soon  be  extinguished,  because 
no  fresh  air  can  enter  from  be- 
low. The  candle  is  also  extin- 
guished when  the  cylinder  is 
covered  at  the  top,  although  the 
cylinder  is  so  held  that  the  air 
can  gain  admittance  from  be- 
low; it  is  extinguished  in  this 
case,  because  the  escape  of  the 
burnt  gases  is  prevented.  If  the 

cylinder  is  placed  uncovered  on  two  pieces  of  wood,  the 
candle  continues  to  burn  quietly,  and  by  holding  a  taper 
recently  extinguished  near  the  lower  opening,  it  will  be 
obvious,  from  the  direction  of  the  smoke,  that  air  rushes 
in  at  the  bottom,  but  escapes  at  the  top,  having  become 
hot  and  lighter  during  the  process  of  combustion. 

The  hand  can  be  held  quite  close  over  the  flame  of  a 
lamp  without  being  burnt,  but  if  the  flame  be  surrounded 
by  the  glass  cylinder,  the  heat  cannot  be  borne,  unless 
the  hand  be  much  farther  removed  from  the  flame.  In 
the  former  case  the  hot  air  radiates  in  all  directions,  while 
in  the  latter  it  is  confined  within  the  walls  of  the  cylin- 
der ;  consequently  the  hot  air  must  issue  from  the  top 
more  rapidly,  and  the  cold  air  enter  more  rapidly  from 
below  to  replace  it.  Owing  to  this  increased  current  of 
air,  cylinders  effect  a  brisker  and  more  perfect  combus- 
tion, and  cause  a  brighter  and  stronger  illuminating 
flame. 

Chimneys  are   to  fire-places  what  cylinders  are  to 
9* 


102 


METALLOIDS. 


Fig.  63. 


lamps.  It  is  well  known  that  narrow  chimneys  draw 
better  than  wide  ones ;  the  air  escapes  from  the  former 
hotter  and  more  rapidly ;  hence  a  greater  quantity  of 
cold  air  is  supplied  to  the  fire,  causing  it  to  burn  more 
freely. 

Experiment.  —  If  the  upper  part  of  the  cylinder  of 
a  lamp  be  divided  into  two 
channels  by  a  partition  down 
the  middle,  the  candle  will  then 
burn,  even  if  access  of  air  be  cut 
off  from  below.  The  smoke 
of  a  glimmering  taper  will  be 
drawn  inwards  on  one  side  and 
expelled  from  the  other,  as  indi- 
cated by  the  arrows  in  the  fig- 
ure ;  a  draught  of  air  sets  in  from 
the  top  to  the  bottom,  which 

supplies  the  oxygen  requisite  for  combustion;  that  this 
current  of  air  exists  is  also  made  evident  by  the  quiver- 
ing motion  of  the  flame. 

112.  In  common  lamps  air  has  access  only  to  the 
outside  of  the  flame;  hence  combustion 
goes  on  only  at  the  circumference,  and  not 
simultaneously  in  the  interior,  as  is  indicat- 
ed by  the  dark  central  portion.  But  if  air 
be  admitted  into  the  interior  of  the  flame, 
this  dark  portion  disappears ;  then  a  more 
complete  combustion  is  effected,  with  the 
production  of  increased  light.  On  this 
principle  the  so-called  Argand  lamps  are 
constructed,  to  which  are  adapted  circular 
wicks,  so  that  the  air  has  access,  not  only  to 
the  exterior  surface  of  the  flame,  but  is  ad- 
mitted from  below  directly  through  the  cen 


Fi«r.  61. 


COMBUSTION. 


105 


Fig.  62. 


tre  of  the  flame,  causing  it  to  burn  in  the  form  of  a  hol- 
low ring.  They  are  also  called  lamps  with  a  double 
draught.  The  so-called  Berzelius  Spirit-Lamp^  universal- 
ly employed  in  chemical  laboratories, 
when  a  higher  heat  is  required  than 
a  common  spirit-lamp  can  yield,  is 
constructed  on  this  principle.  It  is 
made  of  brass  plate,  is  attached  to  a 
brass  stand,  and  is  provided  with 
several  rings  of  various  sizes  for 
holding  porcelain  dishes,  crucibles, 
and  other  vessels,  that  are  to  be 
heated.  In  using  this  lamp,  care 
must  be  taken  that  sufficient  space 
be  left  between  the  vessels  and  the 
chimney  for  the  escape  of  the  hot  air,  and  for  the  diffu- 
sion of  the  upper  part  of  the  flame.  If  this  be  not  done, 
the  combustion  will  be  imperfect,  and  consequently  less 
heat  be  given  out.  When  it  is  desired  to  feed  the  lamp 
with  more  alcohol,  the  flame  must  first  be  extinguished, 
as  otherwise  the  alcohol  might  take  fire  and  cause  seri- 
ous inconvenience. 

113.  In  order  to  kindle    a  substance,    and   to  keep 
it*  continually  burning,  it  must  first  be  heated  to  a  certain 
point,  and  then  maintained  at  this  temperature. 

Experiment.  —  Heat  in  a  small  ves- 
sel some  ashes  or  sand,  on  which  a 
few  friction-matches  have  been  placed; 
the  latter,  or  more  correctly  the  phos- 
phorus on  them,  will  not  inflame  until 
the  ashes  are  heated  to  about  65  -70° 
C.,  which  can  be  readily  ascertained 
by  the  thermometer. 

114.  Slow  and  rapid  Combustion.  —  Experiment.  —  If 


Fig.  63. 


104  METALLOIDS. 

a  coil  of  fine  platinum  wire,  being  raised  to  a  white  heal 
in  the  flame  of  a  spirit-lamp,  be  plunged 
quickly  into  a  heated  goblet  into  which 
a  teaspoonful  of  strong  alcohol  has  been 
poured,  it  will  continue  to  glow  in  the  va- 
por of  the  alcohol,  whilst  it  would  soon  have 
ceased  glowing  in  the  air.  The  alcohol  un- 
dergoes a  slow  combustion,  that  is.  it  unites 
with  a  small  quantity  of  oxygen,  and  the 
heat  thus  liberated  is  sufficient  to  keep  the 
wire  red-hot.  A  disagreeable  sour  smell  will  also  be 
perceived,  proceeding  from  the  new  combination  formed 
between  the  alcohol  and  oxygen  during  the  slow 
combustion,  and  which  may  be  regarded  as  partially 
burnt  alcohol.  When  alcohol  is  kindled,  it  burns  briskly 
and  completely,  and  the  products  emit  no  smell ;  there- 
fore the  combinations  formed  daring  the  rapid  or  com- 
plete combustion  must  be  different  from  those  formed 
during  the  slow  or  incomplete  combustion.  Something 
similar  to  this  is  perceived  with  all  other  combustible 
bodies.  The  unpleasant  odor  caused  by  the  singeing 
of  the  hair,  the  scorching  of  wool,  the  boiling  over  of 
milk,  and  the  dull  burning  of  blotting-paper,  is  the  conse 
quence  of  incomplete  combustion ;  if  they  had  been  com- 
pletely burnt,  no  bad  smell  would  have  been  observed. 
If  in  the  last  experiment  ether  be  substituted  for  alco- 
hol, and  the  wire  be  brought  to  a  white  heat,  it  will 
cause  it  to  burst  into  flame ;  but  the  red-hot  wire  will 
not  kindle  it.  The  temperature  of  the  red-hot  wire  is 
not  sufficient  to  produce  rapid  combustion  of  the  ether, 
but  a  stronger  heat  is  required.  As  phosphorus  did 
not  inflame  until  it  was  heated  to  70 D  C..  nor  ether  un- 
til a  higher  temperature  was  attained,  so  all  combusti- 
ble substances  require  a  certain  degree  of  heat  at  which 


COMBUSTION. 

to  enter  into  rapid  combustion,  some  a  higher  and  some; 
a  lower  degree.  When  burning  bodies  are  cooled  below 
this  temperature,  they  are  extinguished.  Red-hot  iron 
wil1  continue  to  burn  in  oxygen,  but  not  in  common 
air  heat  enough  is  evolved  during  the  combustion  in 
oxygen  to  keep  it  burning,  while,  in  the  five  times  slow- 
er combustion  in  the  air,  sufficient  heat  is  not  evolved 
for  the  continuance  of  this  process.  Pit-coal  requires 
for  sustained  combustion  a  stronger  heat  than  wood ; 
therefore  the  pieces  must  lay  close  upon  each  other  in 
the  grate  or  stove,  or  they  will  cool  off  too  much  and 
cease  burning ;  wood  continues  to  burn,  even  when  » 
spread  loosely  about  on  the  hearth  of  the  stove.  A 
glowing  coal  is  extinguished  much  sooner  when  placed 
on  iron  than  on  wood,  for  the  iron,  a  good  conductor 
of  heat,  withdraws  the  warmth  more  rapidly  than  wood, 
a  bad  conductor. 

Even  the  flame  of  a  candle,  or  of  a  spirit-lamp,  can  be 
cooled  to  such  a  degree  by  iron  as  to  be  extinguished. 
Experiment.  —  If  you  introduce  a  piece  of  wire  gauze, 
such  as  is  used  for  sieves,  into  the 
flame  of  a  lamp,  this  will  be  sup- 
pressed as  though  a  piece  of  tin- 
plate  were  held  over  it,  and  smoke, 
but  no  flame,  passes  through  the 
net-work.  This  smoke,  if  kindled 
by  a  match,  will  again  burn.  The 
smoke  in  passing  through  the  iron 
gauze  has  become  cooled  down  be- 
low the  temperature  necessary  for 

burning;  if  this  temperature  be  restored  by  the  applica- 
tion of  a  taper,  or  by  the  gauze  having  reached  a  white 
heat,  the  smoke  is  again  kindled. 

An  illustrious  English  chemist  has  made  a  successful 


106  METALLOIDS. 

application  of  this  principle  for  the  prevention  of  the  ex- 
plosions so  often  occurring  in  coal  mines.  In  many 
mines  a  combustible  gas  (fire-damp,  or  light  carburetted 
hydrogen)  issues  from  the  fissures  of  the  coal,  which, 
mixing  with  the  atmospheric  air,  forms  an  explosive  gas, 
which  might  be  fatal  to  the  miner  who  should  carry  a 
burning  lamp  into  a  vein  filled  with  such  a  gas.  But 
if  the  flame  be  inclosed  within  an  iron  net-work,  the  ex- 
plosive gas  would  only  burn  within  the  cage  ;  the  miner 
thus  warned  has  time  to  withdraw,  and  this  dangerous 
gas  is  afterwards  expelled  by  appropriate  means.  (Da- 
vy's Safety-lamp.) 

115.  Complete  Combustion.  —  In  the  combustion  of 
hydrogen,  water  is  formed  (§  87),  and  in  the  combustion 
of  carbon,  carbonic  acid  (§§  63,  109).  Both  of  these 
products  are  also  formed  in  the  combustion  of  most 
other  substances  familiar  to  us,  as  these  generally  con- 
tain hydrogen  and  carbon,  on  which  depends  their  ca- 
pacity for  burning. 

Experiment.  —  Invert  an  empty  flask  over  a  burning 
candle,  so  that  it  may  receive  the  hot  gases 
as  they  form ;  it  becomes  clouded  on  the  in- 
side, from  the  deposition  of  moisture  which  is 
condensed  from  the  smoke  upon  the  cold  sur- 
face of  the  glass.     This  smoke  consequently 
contains  vapor.     This  explains  why,  on  heat- 
ing a  vessel  over  a  lamp,  moisture  is  depos- 
ited on  the  outside  as  long  as  it  remains  cold. 
Pour  lime-water  into  the  flask,  and  agitate  it. 
The  liquid  will  become  turbid,  and  deposit, 
or  standing,  a  white  powder  (carbonate  of  lime) ;  thus 
the  smoke  contains  also  carbonic  acid;  some  nitrogen 
also  must  of  course  be  present,  as  it  existed  in  the  at- 
mospheric air  which  was  used  in  maintaining  the  fire 


COMBUSTION.  107 

These  component  parts  exist  likewise  in  the  smoke 
which  issues  from  the  chimneys  of  houses,  whether 
formed  from  the  combustion  of  wood,  pit-coal,  or  brown 
coal ;  and  are  contained  in  the  invisible  current  which 
ascends  from  an  alcohol  or  oil  flame. 

116.  Incomplete  Combustion.  —  Experiment.  —  Tf  you 
extinguish  a  lighted  candle  having 
a  long  snuff,  you  can  rekindle  the 
smoke  ascending  from  the  wick, 
even  at  some  distance  ;  this  smoke 
consists  of  the  combustible  gases 
into  which  the  tallow  has  been 
converted  by  heating.  It  is  par- 
tially consumed  tallow,  and  has -an 

unpleasant  smell.  On  being  extinguished,  sufficient 
heat  is  not  retained  for  its  complete  combustion,  but 
this  commences  again  when  the  smoke  is  heated  and 
kindled  by  a  match.  Completely  burnt  tallow,  that  is, 
tallow  converted  into  carbonic  acid  and  w^ater,  has  no 
smell. 

Experiment.  —  If  you  stop  up  the  draught  of  a  burn- 
ing astral  or  Argand  lamp  (§  112)  with  a  piece  of 
paper,  the  flame  will  immediately  become  dark  and 
red,  emitting  a  thick  black  smoke,  which  has  a  very  dis- 
agreeable odor,  and  which  covers  a  piece  of  paper  held 
over  it  with  soot.  There  is  an  incomplete  combustion  of 
the  oil,  owing  to  the  exclusion  of  the 
air;  a  part  of  the  carbon  contained 


in  the  oil  remains  unconsumed,  and 
escapes  as  soot. 

Experiment. — Refrigeration  gives 
rise  to  the  same  phenomenon,  as 
for  example,  when  an  iron  spoon 
is  held  over  the  flame  of  a  com- 


108  METALLOIDS. 

mon  oil-lamp,  so  as  partly  to  suppress  it.  The  iron 
being  a  good  conductor,  not  only  cools  the  flame,  but 
it  also  obstructs  the  draught  of  air  ;  a  part  of  the  car- 
bon, therefore,  remains  unconsumed,  and  is  deposited 
as  soot  upon  the  spoon.  In  this  way  watchmakers  pre- 
pare lamp-black  for  marking  their  dial-plates.  A  tal- 
low candle  yields  an  invisible  and  scentless  smoke 
when  allowed  to  burn  quietly,  but,  on  the  contrary,  a 
sooty  and  disagreeably  smelling  smoke  when  the  flame 
is  cooled  by  blowing  upon  it,  or  moving  the  lamp  about. 
In  order  to  smoke  meat  rapidly,  green  or  wet  wood  is 
burnt;  this  yields  a  thick,  black  smoke,  because  it  can- 
not be  heated  above  100°  C.  as  long  as  it  contains 
warter,  and  at  this  low  temperature  it  is  only  incom- 
pletely consumed. 

117.  Illuminating'  Gas  and  Flame.  —  Experiment.  — 
To  acquire  a  clearer  understanding  of  the  products  of 
incomplete  combustion,  put  into  a  large 
test-tube  some  wood-shavings,  and  heat 
it,  having  previously  adapted  to  the 
opening  a  cork,  provided  with  a  glass 
tube  or  a  piece  of  pipe-stem  (Fig.  69). 
The  gaseous  matter  which  is  formed 
will  pass  through  the  tube,  and,  on  be- 
ing kindled,  will  burn  with  a  luminous 
flame.  Previously  to  being  kindled,  the 
shavings  emit  a  sour  and  ernpyreumatic 
odor ;  this  smell,  however,  vanishes  en- 
tirely on  burning.  Flame,  then,  is  causea 
by  burning  gas.  Substances  which  do  not  become 
gaseous  on  combustion  can  only  glow,  but  cannot 
burn  with  a  flame.  Some  charcoal  will  remain  un- 
burnt  in  the  test-tube,  owing  to  a  deficiency  in  the  sup- 
ply of  air.  An  application  of  this  principle  is  made 


COMBUSTION. 


109 


Fig.  70. 


on  a  large  scale  in  the  preparation  of  illuminating  gas 
by  the  heating  of  pit-coal,  rosin,  &c.,  in  closed  iron  ves- 
sels. Every  candle  and  every  oil-lamp,  when  burning, 
are  generators  of  gas  on  a  small  scale. 

118.  Experiment.  —  Repeat  the  experiment  with  pul- 
verized   pit-coal, 
but  conduct  the 
gas,     through    a 
bent  glass  tube, 
into  a  jar  placed 
over  the  pneuma- 
tic  trough,    and 
collect  it  as    al- 
ready   described. 
The  gas  is  color- 
less, and  on  be- 
ing ignited  burns 
like  hydrogen,but 
with  a  far  more 
luminous    flame. 
Its  chief  constit- 
uent is  indeed  hydrogen,  chemically  united  with  some 
carbon  (carburetted  hydrogen  gas).      During  combus- 
tion, both  constituents  of  illuminating  gas  unite  with 
the  oxygen  of  the  air,  and  are  converted  into  carbonic 
acid  and  water. 

Coke,  already  alluded  to,  which   is  a  tolerably  pure 
carbon,  remains  behind  in  the  tube. 

Carbon  forms  with  hydrogen  a  very  numerous  cla>,- 
ot  chemical  compounds  ;  those  with  which  we  are  best 
acquainted  are,  —  a)  light  carburetted  hydrogen  (H.  C), 
which  issues  from  the  fissures  of  many  coal-beds  (lire- 
damp,  §  114),  and  is  likewise  always  generated  wher- 
ever vegetable  matter  is  putrefying  under  water  (marsh 
10 


110 


METALLOIDS. 


gas,  §  446) ;  owing  to  its  larger  proportion  of  hydrogen, 
it  is  lighter,  and,  on  account  of  its  smaller  proportion  of 
carbon,  it  burns  with  a  paler  (lame,  than  b)  heavy  car- 
buret ted  hi/drogen  (H4  C^),  commonly  called  olefiant  gas 
(§503).  These  two  gases  (H,  C  and  H4  C<)  form  the 
principal  constituents  of  the  common  illuminating  gas. 
119.  Experiment.  —  Heat  some  pieces  of  wood,  and 
conduct  the  volatile  matter  through  a  tube  into  a  flask 
immersed  in  cold  water,  and  adapt  to  the  cork  of  the  lat- 

Fig.  71. 


ter  another  open  tube,  for  the  escape  of  the  illuminating 
gas.  Two  fluids  will  be  condensed  at  the  bottom  of 
the  flask;  one  a  very  thick  viscid  fluid,  and  the  other  a 
thinner  watery  substance.  The  first  is  called  wood- 
tar;  it  is  resinous,  and  is  therefore  insoluble  in  water. 
The  other  is  called  woo&vinegar,  or  pyroligneous 
acid ;  both  its  taste  and  action  upon  blue  test-paper  in- 
dicate that  it  is  an  acid.  Illuminating1  g*as,  wood-tar, 
and  wood-vinegar  did  not  previously  exist  in  the  wood, 
but  were  formed  during  the  incomplete  combustion 
from  its  constituent  parts,  carbon,  hydrogen,  and  oxy- 
gen. Such  new-formed  substances  are  called  products; 
and  in  the  present  case,  moreover,  products  of  the  in- 


COMBUSTION.  Ill 

complete  combustion  (dry  distillation)  of  wood.  11} 
drogen  predominates  in  illuminating  gas;  oxygen  in 
pyroligneous  acid  ;  and  carbon  in  wood-tar ;  all  of  them, 
owing  to  the  deficient  supply  of  air,  were  but  partially 
burnt,  and  they  are  hence  capable  of  undergoing  further 
combustion  in  t-he  air,  and,  like  the  wood  from  which 
they  originated,  of  being  fully  converted  into  carbonic- 
acid  and  water.  A  portion  of  wood  always  remains  in- 
completely consumed  in  our  fire-places,  and  therefore 
soot  is  deposited  in  the  funnels  and  chimneys ;  the  tar 
and  acid  are  also  deposited,  as  a  black  shining  sub- 
stance, upon  the  jambs  of  the  chimney. 

The  operation  by  which,  as  in  the  present  case,  liquid 
products  may  be  obtained  from  a  solid  substance,  is 
called  dry  distillation.  Most  of  these  liquids  have  a 
brown  color,  and  a  peculiar,  unpleasant,  empyreumatic 
smell  and  taste. 

120.  It  has  been  previously  stated  that  hydrogen 
burns  very  easily,  and  with  a  flame,  while  carbon  burns 
more  difficultly,  and  without  flame ;  thus  is  easily 
explained  why  fuel  burns  with  a  flame  at  the  com- 
mencement of  the  combustion,  but  finally  only  glows  ; 
it  is  the  hydrogen  which  first  burns  with  a  flame,  and 
afterwards  the  carbon,  with  a  mere  glow,  without 
flame.  All  combustible  substances  that  contain  hydro- 
gen and  carbon  burn  in  a  similar  manner.  Burning 
wood  presents  the  most  convincing  illustration  of  this 
fact. 

121.  The  alcohol  flame  consists  of  two 
parts ;  the  dark  central  part  is  alcohol  vapor, 
and  the  bright  envelope  is  alcohol  vapor 
uniting  chemically  with  the  oxygen  of  the 
air*  The  tapering  form  of  the  flame  is  ow 
ing  to  the  ascending  of  the  hot  gases,  and 


112 


METALLOIDS 


the  rushing  in  of  cold  air  from  below.  The  alcohol 
is  drawn  up  from  the  lamp  by  the  capillarity  of  the 
wick  (§  106) ;  it  burns  with  a  feeble  lustre,  but  if  a 
twisted  wire  or  some  other  solid  body  be  introduced 
into  it,  it.  will  then  burn  vividly.  If  a  thin  wire  is 
placed  across  the  flame,  it  will  be  heated  to  redness 
near  the  margins  of  the  flame,  while  in  the  interior  it 
will  remain  dark  ;  consequently,  the  external  part  is 
much  hotter  than  the  central  part  of  the  flame.  The 
point  of  greatest  heat  is  indicated  by  the  mark  in  the 
figure,  and  vessels  to  be  heated  over  the  spirit-lamp 
should  never  be  placed  below  this  point.  This  may  be 
rendered  very  evident  by  applying  a  friction-match  to 
this  part  of  the  flame,  when  it  will  take  fire  at  once ; 
but  not  so  quickly  if  thrust  into  the  centre  of  the  flame. 
122.  In  the  flame  of  a  lamp  or  candle,  three  portions  can 
be  distinguished ;  in  the  middle  (a,  Fig.  73), 
the  dark  centre,  consisting  of  illuminating  gas 
(decomposed  tallow) ;  around  this  (b),  the 
luminous  cone,  consisting  of  burning  hydro- 
gen, intimately  mixed  with  carbon  at  a  white 
heat;  and  on  the  very  outside  (c),  a  thin, 
scarcely  perceptible  veil,  in  which  carbon  is 
burning.  If  a  horizontal  section,  through  the 
centre  of  the  flame,  be  supposed,  it  would 
present  nearly  the  same  appearance  as  in 
Fig.  74.  The  middle  circle  is  carburetted 
74  hydrogen,  or  illuminating  gas ;  the 

hydrogen  of  which  burns  first,  and 
the  great  warmth  thus  evolved  brings 
the  garbon  to  a  white  heat  (this 
is  indicated  by  the  second  circle) ; 
and  finally,  in  the  exterior  circle,  the 
carbon  is  consumed.  The  heated 


Fig.  73. 


•    RETROSPECT    OP    THE    ORGANOGENS.  113 

carbon  in  the  second  ring  imparts  to  the  fl\me  its 
illuminating  power,  just  as  the  glowing  wire  -Midorcd 
the  alcohol  flame  luminous.  If  a  cold  knife  be  intro- 
duced into  the  flame,  a  portion  of  the  carbon  will  be  so 
much  cooled  that  it  cannot  burn,  and  will  be  deposited 
upon  the  knife  in  the  form  of  soot.  If  a  wire  be  held 
through  the  flame,  the  glowing  part  at  the  hot  margins 
will  remain  clear,  while  soot  will  be  deposited  upon 
that  part  of  it  which  is  in  the  interior  of  the  flame. 

The  brightness  of  a  flame  always  depends,  as  the 
foregoing  experiments  show,  upon  the  presence  of  a 
solid  body,  usually  soot,  which  glows  in  the  flame  ;  if  it 
be  only  heated  to  redness,  the  flame  will  give  out  a 
smoky  red  light,  but,  on  the  contrary,  a  brilliant  light 
when  heated  to  a  white  glow. 


The  four  simple  substances  now  treated  of  form  the 
chief  elements  of  plants  and  animals,  and  are  hence 
called  Organogens  (generators  of  organic  bodies). 


EETKOSPECT   OF  THE   ORGANOGENS  (OXYGEN,  HYDRO- 
GEN, NITROGEN,  AND  CARBON). 

1.  As  we  distinguish  on  a  small  scale,  within  our- 
sel;/es,  body  and  spirit,  so  we  distinguish   also   on    a 
great  scale,  in  nature,  matter  (body)  and  forces  (spirit). 

2.  All  matter  is   ponderable.     Absolute  weight   de- 
termines the  actual  weight  of  a  body  in  the  air ;  spe- 
cific weight  the  relative  weights  of  substances  of  equal 
bulks. 

3.  Bodies  occur  in  three  aggregate  states ;  they  are 
either  solid,  liquid,  or  aeriform. 

4.  The  earth  may  be  regarded  as  the  representative 

10* 


114  METALLOIDS. 

of  solid  bodies ;  water,  of  liquid  ;  air,  of  aeriform  bodies 
and  fire,  as  the  type  of  the  natural  forces. 

5.  The  single  particles  of  bodies  are  held  together  by 
a  power  called  cohesion.     It  is  strongest  in  solid,  and 
weakest  in  aeriform  substances. 

6.  This  force  is  weakened  by  heat,  strengthened  by 
cooling;  bodies  are  expanded  by  heat7  and  the  single 
particles  are  removed  from  each  other ;  by  cooling,  on 
the  contrary,  they  are  again  contracted  into  a  smaller 
space. 

7.  Heat  also  changes  the  aggregate  state  of  bodies , 
it  renders  solid  bodies  liquid  (melting),  and  liquid  bod- 
ies aeriform  (evaporation,  boiling). 

8.  On  cooling,  gaseous  bodies  become  fluid  (distil- 
lation, rain),  fluids  become  solid  (hardening,  freezing). 

9.  On  the  melting  and  evaporation  of  solid  and  fluid 
bodies,  heat  becomes  combined  or  latent  (production  of 
cold)  ;  on  the  freezing  of  fluid  and  the  condensation  of 
gaseous  substances,  heat  becomes  free  (production  of 
heat). 

10.  All  bodies  contain,  accordingly,  latent  heat,  and 
the  fluids  always  less  than  the  gaseous. 

11.  Solid  bodies  also  become  fluid  by  solution  in   a 
liquid.     If  they  separate  again  from  such  solutions  in  a 
regular  form,  they  are  said  to  be  crystallized.     Movable 
ness  and  time  are  necessary  for  crystallization. 

12.  Gaseous  bodies  which  on  cooling  easily  become 
liquid,   are  called   vapors;   those  which  are  converted 
into  liquids  with   difficulty,   or  not  at  all,   are  called 
gases. 

13.  Cohesion  of  bodies  can  also  be  destroyed  by  cut- 
ting, breaking,  &c. ;  hereby  their  form  only  is  changed, 
their  original  constitution  remaining  the  same.     These 
are  exterior  or  mechanical  changes. 


RETROSPECT    OF    THE    ORGANOGENS.  1 

» 

14.  Bat  changes  also  occur  by  which  bodies  are  so 
entirely  altered  in  their  constitution  and  properties,  that 
they  can  no  longer  be  recognized  as  the  original  bodies, 
but  must  be  regarded  as  new  bodies.     These  are  inte- 
rior or  chemical  dianges. 

15.  A  power,  more  or  less  inherent  in  all  bodies,  is 
regarded  as  the  cause  of  the  chemical  changes  ;  it  is 
called  affinity,  or  elective  affinity.     In  inanimate  or  inor- 
ganic bodies  this  power  rules  unrestrained,  but  in  living 
or  organic  bodies  it  is  regulated  by  the  vital  power  of 
vegetables  and  animals. 

16.  Affinity  acts  only  at  insensible  distances ;  when 
matter  is  in  the  closest  contact. 

17.  Affinity  is  stronger  between  bodies  in  proportion 
to  their  greater  dissimilarity,  and  so  much  the  weaker 
the  more  they  are  alike. 

18.  Chemical  changes  may  be  produced  in  two  ways ; 
either  by  the  combination  of  simple  bodies  into  com- 
pound ones  (synthesis),  or  by  the  separation  of  the  com- 
pound bodies  into  their  constituent  parts  (analysis). 

19.  By  analysis   bodies  are   finally   obtained   which 
can  be  no  further  decomposed ;  these  are  called  simple 
bodies  or  chemical  elements.     About  sixty  of  them  only 
are  as  yet  known.     One  element  cannot  be  converted 
into  another. 

20.  Almost  every  chemical  compound  may  be  decom- 
posed by  electricity  or  galvanism. 

21.  By  heat,  the  affinity  of  bodies  for  each  other  is 
sometimes  strengthened,  sometimes  weakened;  heat  as- 
sists both  in  combining  and  in  decomposing  bodies. 

22.  All  chemical  combinations  take  place  according 
to  fixed  measure  and  weight.     This  conformity  to  la\\ 
also  prevails  where  substances  combine  together  in  sev 
eral  proportions  (degrees  of  oxidation,  &c.). 


116 


METALLOIDS. 


23.  Heat    is    evolved    during    almost    all    chemical 
changes,  and   not  unfrequently  gives  rise   to  the  phe- 
nomenon of  fire  (combustion). 

24.  What  is  ordinarily  called  combustion  is  a  combi- 
nation of  carbon  or  hydrogen  with  the  oxygen  of  the 
air,  —  an  oxidation. 

25.  To  oxidize  signifies  to  combine  a  body  with  ox- 
ygen.     The  body  combined  with  oxygen  is   (in  the 
wider  sense)  called  an  oxide. 

26.  There  are  two  different  sorts  of  oxidation,  acid 
and  basic ;  the  metalloids  form  with  oxygen,  by  prefer- 
ence, acids ;  the  metalsy  by  preference,  bases  (oxides  in 
the  narrower  sense). 

27.  Acids  and  bases  have   a  very  great  affinity  for 
each  other;  when  they  combine  together,  the  acid  prop- 
erties of  the  former  and  the  basic  properties  of  the  lat- 
ter disappear  (neutralization).     The  newly  formed  body 
is  called  a  salt. 

28.  The  chemical  elements  are  designated  by  the  in- 
itial letters  of  their  Latin  names  (chemical  symbols) ; 
from   the   latter    chemical   formulas    are    constructed, 
which  represent  concisely  the  constitution  of  the  com- 
pound bodies. 

X 

SECOND   GROUP  OF  METALLOIDS:    PYROGENS. 

BRIMSTONE,  SULPHUR  (S). 
At.  Wt.  =  200.  —  Sp.  Gr.  =  2.0. 

123.  SULPHUR,  an  article  very  familiarly  known, 
.which,  on  account  of  its  easy  combustibility,  is  em- 
ployed in  the  manufacture  of  matches,  &c.,  has  nei- 
ther taste  nor  smell.  It  has  no  taste,  since  it  is  not 
soluble  in  waiter.  When  we  throw  some  flowers  of 
sulphur  into  cold  or  hot  water,  it  is  not  dissolved.  We 


SULPHUR.  11 V 

perceive  taste  only  in  such  bodies  as  can  be  dissolved 
in  water,  since  they  alone  will  dissolve  in  the  saliva; 
for  example,  there  is  taste  in  salt  and  sugar,  but 
none  in  insoluble  substances,  as  stones,  charcoal,  starch, 
&c.  Sulphur  has  no  smell,  as  it  does  not  volatilize 
at  the  ordinary  temperature.  We  can  only  perceive 
smd;  in  a  body  when  volatile,  consequently  gaseous 
or  vaporous  particles,  are  given  off  from  it,  and  come 
in  contact  with  the  lining  membrane  of  the  nose. 

124.  Experiment.  —  Sulphur  is  fusible.     Heat   two 
ounces  of  flowers  of  sulphur   in  a  small   stone-ware 
crucible,  over  a  spirit-lamp ;  it  is  'converted,  at  a  temper- 
ature a  little  above  that  of  boiling  water,  into  a  thin, 
brownish  fluid.    If  you  pour  some  of  it  into  cold  water, 
you  obtain  again   solid  sulphur.     If  this,   after  being 
previously  dried,  is  returned  to  the  crucible,  it  will  sink 
in  the  fluid  mass,  showing  that  solid  is  heavier  than 
melted  sulphur.     Almost  all  other  bodies  behave  in  the 
same  manner ;  ice,  which  floats  on  water,  being  an  ex- 
ception. 

125.  Experiment.  —  Sulphur  may  be  crystallized.    Let 

the  crucible  containing  the  melted  sulphur 
stand  till  a  crust  has  formed  over  the  surface ; 
break,  this  quickly,  and  pour  out  the  portion 
remaining  fluid.  Upon  afterwards  breaking 
the  crucible,  the  cavity  of  the  sulphur  will  be 
found  lined  with  fine  crystals,  in  the  form  of 
lengthened  pillars  (Fig.  75),  which  are  called 
oblique  /rhombic  prisms.  This  is  the  second 
method  of  forming  crystals,  and  differs  from  the 
mode  of  obtaining  those  of  saltpetre  and  salt 
(§§50,  52),  inasmuch  as  in  the  one  case  the 

body  was  rendered  liquid  by  solution,  in  the  other  by 

heat. 


118  METALLOIDS. 

If  the  sulphur  is  allowed  to  cool  quietly,  without  de« 
canting  the  liquid  portion,  this  also  will  become  solid,  and 
such  a  dense  mass  of  crystals  will  be  formed,  that  there 
will  be  no  vacant  space  between  them.  This  mass,  on 
being  fractured,  presents  a  glistening  appearance,  owing 
to  the  reflection  of  light  from  the  surfaces  of  the  minute 
crystals.  Such  a  body  is  said  to  be  crystalline,  or  to 
have  a  crystalline  structure. 

126.  In  different  parts  of  the  world,  particularly  in 
volcanic  countries,  large  beds  of  sulphur  (native  sul- 
phur) are  not  un frequently  found,  and,  in  these  beds, 
fissures  and  cavities  studded  with  the  most  beautiful 
crystals,  which  required,  perhaps,  centuries  for  their  for- 
mation. These  native  crystals  have  a  very  different 
76  form  from  those  artificially  prepared.  They 
occur  in  pointed  four-sided  pyramids,  applied 
base  to  base  (Fig.  76) ;  such  a  form  is  called 
an  acute  octahedron,  because  contained  undei 
eight  acute  triangles.  Thus  sulphur,  like  car- 
bon in  diamond  and  graphite,  assumes  two 
different  forms  ;  it  is  dimorphous. 

127.  Experiment.  —  Sulphur  may  be  made  to 
assume  a  still  different  state.     Heat  a  test-tube,  support- 
^  ed  by  means  of  a  wire  twisted  round 

it,  and  filled  with  powdered  sulphur, 
over  a  spirit-lamp ;  on  fusing,  the  sul- 
phur runs  together,  so  that  it  only  half 
fills  the  tube.  The  sulphur  first  be- 
comes thin,  like  water,  but  on  further 
heating  it  becomes  brown,  and  so 
thick  and  viscid  that  the  tube  may  be 
inverted  without  the  sulphur  flowing 
out.  Thrown  into  water  while  in 
this  condition,  it  forms  a  transparent,  soft,  elastic  mass, 


SULPHUR. 

which,  after  a  few  days,  is  reconverted  into  solid  sul 
phur.  This  sulphur,  resembling  melted  glass,  is  said 
to  be  amorphous,  a  term  applied  to  all  other  bod- 
ies, having  no  regular  form  ;  such  as  gum,  pitch, 
glue,  &c. 

128.  Experiment.  —  If  the  sulphur  in  the  test-tube  be 
Fitr  73  heated  still  more  strong- 

ly, at  a  temperature,  per- 
haps, four  times  above 
that  of  boil  ing- water,  it 
begins  to  boil,  and  is 
thereby  converted  into  a 
reddish-brown  vapor,  sul- 
phur fumes ;  thus  sulphur 
is  volatile,  and  may,  like 
water,  assume  all  the 

three  states  of  aggregation  (solid,  fluid,  and  aeriform) 
Sulphur  is  twice  as  heavy  as  water,  and  the  fumes  six 
and  a  half  times  heavier  than  common  air.  Within 
the  tube,  the  fumes  of  sulphur  are  transparent,  and 
have  a  reddish-brown  color  ;  but  after  escaping,  on 
the  contrary,  they  appear  as  a  yellowish  smoke,  being 
condensed  by  the  cold  air  into  a  dust  of  solid  sulphur. 
If  these  fumes  be  conducted  into  a  glass  jar,  immersed 
in  cold  water,  the  sulphur  condenses  in  it  in  the  form  of 
a  soft  yellow  powder,  known  in  commerce  by  the  name 
of  flowers  of  sulphur.  In  the  preparation  of  sulphur  on 
an  extensive  scale,  the  operation  is  conducted  in  large 
chambers.  The  process  by  which  a  volatile  substance 
is  evaporated  and  condensed  again  into  a  solid  is 
called  sublimation.  In  distillation,  the  vapor  is  con- 
densed into  liquid  (the  distillate),  in  sublimation,  into  a 
solid  (the  sublimate). 

If,  in  this  experiment,  the  receiver  were  not  kept  cool 


120  METALLOIDS. 

it  would  gradually  become  so  hot  that  the  sulphu. 
would  pass  over  as  a  fluid,  and  on  this  principle  native 
sulphur  is  purified  on  a  large  scale.  The  earthy  im- 
purities, not  being  volatile,  remain  behind  while  the 
sulphur  is  distilled  over,  and  again  condensed.  The 
melted  sulphur  is  commonly  poured  into  moistened 
wooden  moulds,  and  is  then  called  roll-sulphur. 

129.  Experiment.  —  Fill  a  test-tube  half  full  of  soap- 
boiler's lye ;  add  to  it  as  much  flowers  of  sulphur  as  can 
be  taken  up  on  the  point  of  a  knife,  and  boil  the  mixture 
for  some  time ;  a  part  of  the  sulphur  will  be  dissolved, 
imparting  to  the  liquid  a  yellowish-brown  color.  The 
clear  liquid  is  now  decanted,  diluted  with  water,  and 
vinegar  added  to  it ;  it  will  immediately  assume  a  milky 
appearance,  owing  to  the  separation  of  the  sulphur  in 
the  form  of  an  exceedingly  fine  powder,  which  is  so 
light  that  a  considerable  time  mast  elapse  before  it  will 
subside.  Collect  the  powder  on  a  filter,  wash  it  with 
water,  and  dry  it  at  a  gentle  heat.  It  is  called  milk  of 
sulphur ',  or  precipitated  sulphur,  and  is  sulphur  in  its 
finest  state  of  subdivision,  caused  by  the  separation  of 
each  of  its  particles  by  the  water.  Precipitated  sulphur 
has  a  pale  yellowish  tint,  but  on  being  melted,  it  be- 
comes distinctly  yellow,  owing  to  the  union  of  the  single 
particles  into  a  larger  mass.  This  method  is  frequently 
employed  in  chemistry  to  convert  solid  substances  into 
the  finest  powder.  Such  substances  thus  reduced  to  a 
fine  powder  are  not  unfrequently  amorphous. 

The  solution  of  sulphur  in  lye  is  more  complex  than 
that  of  sugar  or  of  salt  in  water ;  as  several  other  pecu 
liar  combinations  of  sulphur  with  the  component  parts 
of  water  are  formed  at  the  same  time.  One  of  them 
sulphuretted  hydrogen  (H  S),  is  gaseous,  and  occasions 
the  offensive  smell  which  is  emitted  on  the  addition  of 


SULPHUR.  121 

vinegar  to  the  solution  of  sulphur.  The  vinegar  unites 
with  the  constituent  of  the  lye,  which  then  loses  its 
power  of  holding  the  sulphur  in  solution. 

130.  Experiment.  —  If  sulphur  be  heated  in  a  vessel 
with  free  access*  of,  air,  for  example,  in  an  iron  spoon, 
or  be  touched  by  some  red-hot  body,  it  burns  with  a 
blue  flame;  that  is,  it  unites  with  the  oxygen  of  the 
air,   under   the   phenomenon   of  fire,  and  forms  with 
the  oxygen,  as  has  been  previously  shown  (§  64),  an  ir- 
ritating gas,  sulphurous  acid  (S  O*).     If  another  atom 
of  oxygen  be  added  to  this,  there  is  then  formed  the 
common    and    very   important   acid,   called   sulphuric 
acid  (S  O3). 

This  property  wrhich  belongs  to  sulphur,  of  igniting 
and  continuing  to  burn  at  a  very  moderate  heat,  is  the 
reason  of  its  being  so  commonly  used  for  all  kindling 
purposes.  By  means  of  it,  other  bodies  of  more  difficult 
combustion  may  be  heated  to  the  temperature  at  which 
they  can  continue  to  burn  (matches,  gunpowder,  fire- 
works, &c.).  The  kindling  of  a  simple  coal-fire  well 
illustrates  how,  by  gradual  transition  from  easily  inflam- 
mable materials  to  those  of  more  difficult  ignition,  the 
latter  are  finally  brought  to  that  degree  of  heat  at  which 
they  will  ignite  and  continue  to  burn.  Thus,  sparks  of 
iron,  thrown  out  by  the  striking  of  the  steel,  ignite  the 
fine  coal  of  the  tinder ;  this  kindles  the  matches,  by 
means  of  which,  first  straw,  then  wood,  and  finally  coal 
itself,  are  brought  to  the  temperature  requisite  for  burn- 
ing. The  following  is  the  scale  in  the  order  of  com- 
bustion :  —  tinder,  sulphur,  straw,  wood,  pit-coal. 

131.  Sulphur  is  the  strongest  chemical  body,  next  to 
oxygen,  and  has,  like  it,  a  powerful  affinity  for  all  other 
elements. 

Experiment.  —  Boil  some  sulphur  in  a  test-tube, 
11 


122  METALLOIDS. 

expose  a  very  thin  copper  plate  to  th* 
brownish  vapor ;  the  copper  will  glow 
vividly  for  some  moments,  lose  its  red 
color  and  flexibility,  become  gray  and 
brittle,  and  weigh  one  quarter  more 
than  before.  The  newly-formed  gray 
crystalline  body  is  called  sulphuret  of 
copper.  Both  elements  have  intimate- 
ly combined,  and  in  fixed  proportions. 
The  properties  of  the  sulphur,  as  well 
as  of  the  copper,  have  entirely  disappeared.  The  great 
heat  produced  is  a  consequence  of  the  chemical  combi- 
nation, since,  in  accordance  with  a  law  of  nature,  heat 
is  evolved  wherever  bodies  chemically  combine  with 
one  another,  but  in  most  cases  the  heat  does  not  amount 
to  actual  glowing  or  combustion. 

In  a  similar  manner  almost  all  other  metals  may  be 
converted  into  sulphur  metals.  We  find  many  of 
these,  however,  already  formed  in  the  earth,  and  min- 
ers call  them  glance,  blende,  or  pyrites.  The  pyrites 
having  the  lustre  of  brass,  and  found  in  almost  all  pit- 
coal,  is  sulphuret  of  iron ;  red  cinnabar  is  sulphuret 
of  mercury,  &c.  The  sulphuret  of  copper,  artificially 
prepared  as  above,  occurs  also  as  an  ore,  and  is  then 
called  copper  pyrites. 

Experiment. —  Mix  three  fourths  of  an  ounce  of  iron- 
filings,  half  an  ounce  of  flowers  of  sulphur,  and  one 
fourth  of  an  ounce  of  water,  in  a  small  vessel,  and  put 
it  in  a  warm  place ;  the  mass  becomes  heated,  the  wa- 
ter evaporates,  and  in  half  an  hour  a  black  powder  will 
be  obtained,  in  which  no  particles  of  iron  or  of  sulphur 
will  be  perceived ;  a  chemical  compound,  sulphuret  of 
iron,  is  formed.  If  the  two  substances  be  mixed  together 
without  water,  no  combination  will  take  place,  unless 


SULPHURETTED  HYDROGEN.  12b 

they  be  heated  to  redness ;  the  water  effects  the  combi- 
nation, by  bringing  the  particles  of  sulphur  and  iron  into 
such  close  contact  that  they  can  attract  each  other.  It 
is,  as  it  were,  the  bridge  by  which  one  body  passes  over 
to  the  other.  , 

Sulphur  has  also  another  resemblance  to  oxygen,  that 
of  combining  with  other  bodies  in  greater  or  less  quan- 
tilies,  according  to  circumstances.  The  quantities  here 
also  are  always  fixed  and  unchangeable  for  every  in- 
dividual combination  (stochiometry).  In  the  simple 
gray  sulphuret  of  iron,  100  ounces  of  iron  are  always 
united  with  57 3-  ounces  of  sulphur;  in  the  yellow  iron 
pyrites  100  ounces  of  iron  always  unite  with  115 
ounces  of  sulphur  (degrees  of  sulphuration)  ;  if  more 
sulphur  is  present,  it  remains  uncombined.  The  degrees 
of  oxidation  are  distinguished  by  the  terms  protoxides, 
sesquioxideS)  and  peroxides ;  in  the  combinations  of  sul- 
phur, when  the  sulphur  predominates,  they  are  called 
sesquisulphurets  and  persulpliurets ;  and  when  the  sul- 
phur is  not  in  excess,  they  are  called  protosvlplnirf'tx ; 
and  in  the  latter  term,  when  there  is  a  deficiency  of 
sulphur,  the  syllable  sub  is  substituted  for  proto. 

The    chemical  symbol   for   sulphur  is  =  S.     Proto 
sulphuret  of  iron  is  expressed  by  the  symbol  Fe  S ;  per- 
sulphuret  of  iron,  by  Fe  S^.     Fe,  the  first  two  letters  of 
the  Latin  word  ferrum,  is  the  symbol  for  iron. 


SULPHURETTED   HYDROGEN,  OR    HYDRO SULPHTTRIC 
ACID  (H  S). 

132.  Experiment.  —  Put  half  an  ounce  of  protosulphu- 
ret  of  iron  (Fe  S)  and  half  an  ounce  of  diluted  sulphuric 
acid  (§  84)  into  a  two-ounce  flask,  and  quickly  stop  the 
flask  with  a  cork,  to  which  a  bent  glass  tube  is  adapted. 


124 


METALLOIDS. 


Fi?.  80. 


Volatile. 


Introduce  the   longer  limb  of  the  tube  into  a  bottle 
filled  with  cold  water.     The  atmos- 
pheric   air    contained    in    the     flask 
and  tube  first  passes  over,  followed 
by  a  very  offensive  gas,  which  dis* 
solves  in  the  water,  to  which  it  like- 
wise imparts  its  fetid  odor  of  rotten 
eggs.     This  gas  is  called  sulphuretted 
hydrogen.     The  decomposition  in  this  case  is  similar  to 
that  effected  in  the  preparation  of  hydrogen  from  iron 
Water  is  decomposed,  its  oxygen  unites  with  the 
iron,  forming  protoxide 
of  iron,  and  this  unites 
with  the  sulphuric  acid, 
forming    green    vitriol ; 
but  the  hydrogen  of  the 
water  escapes,  and  takes 
with  it  as  a  companion 

the  sulphur  contained  in  the  sulphuret  of  iron.  The 
light,  gaseous  hydrogen  possesses  in  a  great  degree  the 
power  of  rendering  other  bodies  aeriform  on  uniting  with 
them,  even  those  which  are  not  volatile  or  have  but  a 
slight  tendency  to  become  so;  just  as  an  eloquent 
speaker  can  communicate  his  enthusiasm  to  a  heavy 
and  indifferent  audience.  Even  carbon,  which  has  never 
been  liquefied,  is  converted  into  a  light  gas  when  com- 
bined with  hydrogen,  as  in  illuminating  gas. 

When  the  disengagement  of  the  gas  ceases,  add  some 
diluted  sulphuric  acid  that  the  gas  may  again  be  gener- 
ated. The  water  is  known  to  be  saturated  with  the  gas, 
when,  on  shaking  the  bottle,  the  finger  by  which  the 
opening  is  closed  is  no  longer  sucked  in,  or,  more  cor- 
rectly speaking,  pressed  in ;  one  measure  of  water  con- 
tains two  and  a  half  measures  of  gas  in  a  saturate-* 


SULPHURETTED  HYDROGEN.  125 

solution.  It  is  put  up  in  small  well-stoppered  bottles, 
which  are  labelled  Hydrosulphuric  Acid.  If  air  be  ad- 
mitted, the  solution  becomes  turbid,  owing  to  the  oxy 

gen  of  the  air  uniting  witl 
the  hydrogen  of  the  sulphu 
retted  hydrogen,  forming 
Fluid,  water,  and  the  consequent 
liberation  of  the  sulphur  aa 
a  fine  powder. 

If,  during  the  evolution  of  the  gas,  the  bottle  of  wa- 
ter be  removed,  the  gas  issuing  from  the  tube  can  be 
ignited  by  a  match  ;  it  burns  with  a  blue  flame,  and 
its  nauseous  odor  is  no  longer  perceptible,  but  is  re- 
placed  by  the   well-known 
odor    of    burning    sulphur. 
Gas-     Both  constituents  unite  with 
the  oxygen  of  the   air,  the 
Vapor,  sulphur    forming     pulphur- 
ous  acid,  and  the  hydrogen 
water. 

The  inhalation  of  sulphuretted  hydrogen  is  detrimental 
to  health ;  hence  precautions  should  be  taken  to  avo'd  it. 
When  experimenting  with  it,  it  is  best  to  do  so  where 
there  is  a  free  circulation  of  air.  A  cloth  moistened 
with  a  little  alcohol,  and  held  before  the  mouth,  is  like- 
wise a  good  protection. 

Sulphuretted  hydrogen  turns  blue  litmus-paper  red, 
it  also  combines  with  many  bases,  and  hence  it  is  an 
arid.  It  has  also  been  called  Hydrothionic  Acid,  from 
two  Greek  words,  signifying  water  and  sulphur.  Thus, 
oxygen  is  not  essential  to  the  acidity  of  a  compound 
since  hydrogen  also  possesses  this  acidifying  principle; 
but  the  latter  produces  acids  with  but  few  elements 
whilst  oxygen  does  with  numerous  elements. 
11* 


126  METALLOIDS. 

133.  Experiments  with  Sulphuretted- Hydrogen  Water 
Experiment    a.  —  Drop   some  sulphuretted-hydrogen 

water  upon  a  bright  silver 
or  copper  coin,  and  upon 
a  piece  of  lead  and  iron 
the  first  three  metals  tar- 
nish quickly,  and  finally 
become  black  ;  they  com- 
bine with  the  sulphur,  forming  a  dark  sulphur  metal, 
whilst  the  hydrogen  escapes ;  the  iron,  on  the  contrary, 
undergoes  no  change.  Pb  is  the  symbol  for  lead, 
plumbum. 

Experiment  b.  —  Put  into  one  test-tube  a  small  portion 

of  litharge,  into  another 
some  ignited  iron-rust,  and 

Solid. 

pour  upon  them  liquid 
Liquid,  hydrosulphuric  acid;  the 
yellow  litharge,  oxide  of 
lead,  becomes  immedi- 
ately black,  an  exchange  of  elements  takes  place, 
the  hydrosulphuric  acid  gives  its  sulphur  to  the  lead 
of  the  litharge,  and  receives  in  return  the  oxygen  of 
the  latter.  Accordingly,  sulphuret  of  lead  and  water 
are  formed,  and  the  offensive  odor  disappears.  In  the 
vessel  containing  the  iron-rust  neither  the  color  nor  the 
smell  is  affected,  —  a  proof  that  no  chemical  change  has 
taken  place. 

Experiment  c.  —  Repeat  the  same  experiment  with  a 
small  Crystal  of  sugar  of  lead  instead  of  the  litharge,  and 
some  green  vitriol  instead  of  the  iron-rust,  together 
with  a  few  drops  of  vinegar,  these  salts  having  been  pre- 
viously dissolved  in  a  large  quantity  of  water ;  the  re- 
sult will  be  the  same  as  in  the  former  experiment.  Su- 
gar of  lead  is  the  acetate  of  the  oxide  of  lead ;  the  salt 


SULPHURETTED     HYDROGEN. 


127 


Solid. 


and  acetic  acid        and  acetic  acid. 


Insoluble. 


of  lead  is  converted  into  suJphuret  of  lead,  which  sub- 
sides sooner  or  later  as  a 
black  precipitate.  When 
this  solution  is  extremely 
Li  uid  diluted,  it  is  only  colored 
brown.  The  acetic  acid 
is  set  free,  and  remains  in 
solution. 

Experiment  d.  —  If  some  lime-water  or  soda  be  added 
to  the  vitriol  solution,  which  in  the  former  experiment 
remained  unaffected  by  the  addition  of  sulphuretted 

hydrogen,  it  will  imme- 
diately assume  a  de^p 
black  color.  The  added 
base  effects,  what  other- 
wise would  not  have  oc- 
curred, a  combination  of 
the  sulphur  with  the  iron, 
and  for  this  reason,  that 
the  new  base  itself  unites  with  the  sulphuric  acid  of  the 
green  vitriol.  The  sulphuric  acid  has  so  great  an  affin- 
ity for  the  protoxide  of  iron,  that  it  will  not  part  with  it 
unless  in  the  presence  of  a  stronger  base,  which  the  lime 
and  soda  have  proved  themselves  to  be.  Lime  is  oxide 
of  calcium,  and  is  represented  by  the  symbol  Ca  O. 

From  these  experiments  the  following  rules  are  de- 
rived :  — 

a.)  Sulphur  in  its  moist  state,  and  when  dissolved  in 
water,  has  a  very  great  affinity  for  metals,  and  converts 
metals,  metallic  oxides,  and  salts  into  sulphur  metals. 

b.)  Most  of  the  metallic  sulphurets  are  insoluble  in 
water ;  hence  sulphuretted  hydrogen  is  peculiarly  adapt- 
ed for  precipitating  metals  from  their  solution,  so  that 
they  can  be  separated  and  collected  by  filtration.  If 


128  METALLOIDS. 

sulphuretted  hydrogen  be  passed  through  a  solution  of 
acetate  of  copper,  sulphuret  of  copper  will  be  precipi- 
tated, and  can  be  separated  by  filtration  from  the  acid. 
All  the  sulphurets  do  not  possess  a  black  color ;  sulphu- 
ret of  antimony  has  an  orange-red  ccior,  sulphuret  of 
arsenic  a  yellow,  and  sulphuret  of  zinc  a  white  color. 
On  this  is  partly  based  the  application  of  sulphuretted 
hydrogen  as  a  re-agent,  that  is,  as  a  means  of  detecting 
many  metals.  Wine  containing  lead  is  blackened  by 
hydrosulphuric  acid,  which  for  this  reason  is  called 
Hahnemanri's  wine-test. 

c.)  Many  metals  are  precipitated  from  their  solutions 
by  the  addition  merely  of  sulphuretted  hydrogen,  £S 
sulphurets ;  for  example,  copper,  silver,  gold,  lead,  mer- 
cury, tin,  antimony,  and  arsenic  (these  are  called  elec- 
tro-negative bodies) ;  and  others  are  not  precipitated 
until  a  stronger  base  is  added ;  for  example,  iron,  zinc, 
manganese,  cobalt,  and  nickel  (these  are  called  electro- 
positive). Sulphuretted  hydrogen  may  accordingly  be 
used  to  separate  one  class  of  metals  from  another ;  it  is 
therefore  an  important  means  of  separation  in  analyt- 
ical chemistry. 

134.  Hydrosulphuric  acid  has,  as  already  mentioned, 
the  formula  H  S,  which  indicates  that  it  is  composed  of 
one  atom  of  hydrogen  and  one  of  sulphur,  and  the  simi- 
larity of  this  formula  to  that  of  water,  H  O,  is  apparent. 
Lead  paper  is  used  for  the  detection  of  sulphuretted 
hydrogen,  by  which  it  is  colored  brown  or  black.     It  is 
made  by  passing  strips  of  paper  through  a  weak  solu- 
tion of  sugar  of  lead  in  water. 

135.  It  is  well  known,  that  during  the  decomposi- 
tion   of    animal  substances,   blood,  urine,  excrements, 
white   of  eggs,  &c.,  a   putrid   odtf*    ;s  evolved ;    this 
is  owing  to  sulphuretted  hydrogen,        ich  is  formed 


SELENIUM. PFOSPHORUS. 

from  the  small  quantity  of  sulphur  contained  in  most 
animal  substances,  and  from  the  hydrogen  of  the  water, 
and  is  diffused  in  a  gaseous  form  in  the  air.  It  will  no 
longer  appear  strange  that  copper  vessels,  if  exposed  to 
such  an  atmosphere,  will  tarnish,  become  brown,  and 
indeed,  finally,  black. 

136.  Sulphur  is  also  met  with  in  vegetable  substances, 
particularly  in  the  leguminous  plants,  —  peas,   beans, 
&c.,  —  and  in  some  acrid  plants,  such  as  mustard  and 
horseradish.     If  these   are   suffered  to   decay,    sulphu- 
retted hydrogen  is  evolved  from  them. 

137.  Finally,  it  remains  to  be  stated  that  this  gas  oc- 
curs also  in  some  mineral  water  s,  as  may  be  recognized 
by  the  smell  and  taste.     Many  of  these  springs,  for  in- 
stance, the  celebrated  springs  of  Aix-la-Chapelle,  are  re- 
sorted  to  by  invalids,  and  are  called  sulphur  springs. 
A  rotten  wooden  pump  or  log  would  convert  an  other- 
wise potable  water,  if  it  should  contain  gypsum,  into 
a  nauseous  sulphuretted  water;   by  removing  the  rot- 
ten  pipe,  the  water  will  again  become  odorless  and 
potable. 

SELENIUM  (Se). 

Selenium  is  an  element  which  has  a  great  resem- 
blance to  sulphur.  It  is  of  rare  occurrence,  and  is  con- 
tained in  the  red  matter  deposited  from  certain  varieties 
of  sulphuric  acid,  especially  after  the  acid  has  been  di- 
luted with  water. 

PHOSPHORUS  (P). 
At.  Wt.  =  400.  —  Sp.  Gr.  =  1.75. 

138.  Great  care  is  required  in   experimenting   with 
phosphorus,  that  it  does  not  take  fire  at  an  unseason- 
able moment,  as  it  continues  burning  with  the  greatest 


130  METALLOIDS. 

violence,  and  might  occasion  dangerous  wounds.  It 
may  catch  fire  even  when  lying  upon  blotting  paper,  par- 
ticularly in  summer-time,  or  by  the  heat  of  the  finger. 
Hence  it  must  be  kept,  and  also  cut,  under  water.  On 
being  taken  from  the  water,  it  should  be  held  by  a  pair 
of  forceps,  or  be  stuck  on  the  point  of  a  knife.  Pru- 
dence also  would  dictate  to  experiment  with  small  quan- 
tities only  at  a  time,  and  to  have  a  vessel  of  water  in 
readiness,  in  which  it  may  be  quenched  in  case  it  should 
catch  fire. 

139.  Phosphorus  is,  in  its  properties,  closely  allied  to 
sulphur,  but  it  has  an  incomparably  more  irritable  tem- 
perament.    Sulphur  may  be  regarded  as  the  phlegmatic 
brother  of  phosphorus.     Phosphorus,  like  sulphur,  melts, 
boils,  evaporates,  and  burns,  but  far  more  easily  and 
rapidly.     In  winter  it  is  brittle,  in  summer  flexible  as 
wax.     When  pure  and  freshly  prepared  it  is  colorless, 
but  after  a  time  it  becomes  yellow,  and  coated  over 
with  a  hydrated  white  crust. 

Phosphorus  is  insoluble  in  water,  but  soluble  in  ether, 
alcohol,  sulphuret  of  carbon,  and  oils. 

Phosphorus  is  an  exceedingly  violent  poison,  and  is  for 
this  reason  frequently  employed  for  +he  extirpation  of 
rats  and  mice.  The  rat  electuary,  so  called,  (phosphorus 
dough,)  is  composed  of  1  dram  of  phosphorus,  8  ounces 
of  hot  water,  and  8  ounces  of  flour.  (See  p.  682.) 

140.  Experiments  with  Phosphorus. 

Experiment  a.  —  Put  into  a  small  flask,  first  a  quarter 
of  an  ounce  of  ether,  then  a  piece  of  phosphorus,  of  the 
size  of  a  pea.  Cork  the  flask  and  let  it  stand  some 
days,  frequently  shaking  it.  Decant  the  liquid ;  it  con- 
tains in  solution  about  one  grain  of  phosphorus,  and 
will  serve  for  the  following  experiments. 

Experiment  b.  —  Pour  some  drops  of  this  solution 
upon  the  hand,  and  rub  them  quickly  together;  the 


PHOSPHORUS.  131 

ether  will  evaporate  in  a  few  moments,  but  the  phos 
phorus  will  remain  upon  the  hands  in  a  state  of  mi 
nutest  division.  The  more  finely  it  is  divided,  so  much 
the  more  easily  does  it  combine  with  the  oxygen  of  the 
air.  ^During  this  combination  it  diffuses  a  white  smoke 
and  a  strong-  light  (it  phosphoresces),  causing  the  hands 
to  shine  in  the  dark;  hence  its  name, phosphorus,  from 
<££$-,  light,  and  </>epetz/,  to  carry.  On  rubbing  the  hands  this 
light  becomes  more  vivid,  as  a  fresh  surface  of  phos- 
ohorus  is  thus  continually  presented  to  the  oxygen  of 
the  air.  The  heat  thus  evolved  is  too  feeble  to  occasion 
ignition.  This  oxidation,  taking  place  at  a  low  temper- 
ature, is  called  sloiv  combustion.  The  hands,  during  the 
phosphorescence,  have  an  alliaceous  smell,  and  impart 
at  the  same  time  a  sour  taste  to  the  tongue,  as  the  com- 
bination of  the  oxygen  with  the  phosphorus  is  an  acid ; 
it  is  called  phosphorous  acid,  and  consists  of  one  atom  of 
phosphorus  and  three  atoms  of  oxygen.  When  a  larger 
quantity  of  acid  is  required,  put  a  stick  of  phosphorus 
into  a  flask,  and  let  it  remain  in  the  cellar  until  the  phos 
phorus  is  converted  into  a  colorless  acid  liquid.  A  por- 
tion of  the  phosphorous  acid  thus  prepared  takes  up  yet 
more  oxygen  and  becomes  phosphoric  acid ;  accordingly, 
the  liquid  thus  obtained  is  a  mixture  of  these  two  acids. 
Experiment  c.  —  Moisten  a  lump  of  sugar  with  the 
solution  of  phosphorus,  and  throw  it  into  hot  water. 
The  heat  of  the  latter  volatilizes  the  ether  and  the  phos- 
phorus, both  of  which  rise  to  the  surface  of  the  water 
and  there  inflame  spontaneously  on  coming  in  contact 
with  the  oxygen  of  the  air.  The  combustion  in  this 
case  is  brisk  and  complete.  The  phosphorus  takes  np 
a  larger  quantity  of  oxygen,  one  atom  of  it  uniting  with 
five  of  oxygen  ;  there  is  formed  phosphoric  acid,  which  is 
always  generated  when  phosphorus  is  completely  burnt, 
that  is,  with  a  flame,  as  has  already  been  explained. 


132  METALLOIDS. 

Experiment  d.  —  Pour  some  of  the  ethereal  solution 
of  phosphorus  upon  fine  blotting-paper ;  the  latter  ig- 
nites spontaneously  after  the  ether  has  evaporated.  The 
more  minutely  the  phosphorus  is  divided,  so  much  the 
more  readily  it  begins  to  burn.  % 

Experiment  e.  —  Put  a  piece  of  phosphorus  of  the  size 
of  a  pea  on  blotting-paper,  and  sprinkle  over  it  some 
soot  or  pulverized  charcoal ;  it  melts  after  a  while,  and 
spontaneously  inflames.  The  finely  pulverized  charcoal 
causes  this  combustion,  owing  to  its  porosity.  It 
eagerly  absorbs  oxygen  from  the  air,  imparts  it  again  to 
the  phosphorus,  and,  being  also  a  non-conductor,  the 
cooling  of  it  is  prevented. 

141.  Phosphorus  is  also  easily  ignited  by  friction,  and 
is,  for  this  reason,  employed  in  the  manufacture  of  fric- 
tion-matches.    The  combustible  mass  is  prepared  from 
hot  mucilage  (70°  C.),  to  which  small  pieces  of  phos- 
phorus are  added,  being  thoroughly  incorporated  with  it 
by  constant  rubbing  till  cold.     But  as  the  mass,  becom- 
ing hard  on  drying,  would  prevent  the  admission  of  air 
to  the  phosphorus,  there  must  be  added  some  substance 
rich  in  oxygen,  as  black  oxide  of  manganese,  nitre,  or 
red-lead,  from  which  the  phosphorus  can  abstract  the 
oxygen  necessary  for  its  ignition.      If  parts  of  phos- 
phorus, 4  of  gum  Arabic,  4  of  water,  2  of  nitre,  and  2  of 
red-lead,  form  a  good  inflammable  mass.     A  tempera- 
ture of  65-70°   C.  is  requisite  for  kindling   matches 
(§  113) ;  in  this  case  the  temperature  is  caused  by  fric- 
tion.    The  coating  of  the  match  is  thus  broken  and 
kindled,  and  the  continued  burning  is  now  maintained 
by  the  oxygen  of  the  air. 

142.  Experiment.  —  Put  a  piece  of  phosphorus,  of  the 
size  of  a  pea,  into  a  wine-glass,  and  pour  hot  water  upon 
it,  until  the  glass  is  half  filled ;  the  phosphorus  melts, 
but  does  not  ignite,  as  access  of  air  is  prevented  by  the 


PHOSPHORUS. 


133 


Fig.  82. 


Fig.  3i.  water.      But   if    air   be  carefully 

blown  by  the  mouth  through  a 
long  glass  tube  upon  the  bottom 
of  the  wine-glass,  a  combustion 
will  ensue  which  is  visible,  espe- 
cially in  the  dark.  The  phos- 
phorus enters  at  once  into  oxida- 
tion, but  with  the  formation  of  a 
lower  compound ;  it  swims  as  a 
red-hot  powder  in  the  liquid,  and 
is  called  oxide  of  phosphorus ,  con- 
taining for  every  two  atoms  of 
phosphorus  only  one  atom  of  oxygen. 

143.  Experiment.  —  We  obtain  the  same  combina- 
-  tion  by  gently  heating  a  piece 
of  phosphorus  of  the  size  of  a 
D  pea,  placed  in  the  middle  of 
a  glass  tube,  about  twelve 
inches  long.  When  ignition 
commences,  remove  the  lamp. 
While  the  tube  is  held  hori- 
zontally, the  combustion  is  fee- 
ble and  imperfect,  because  the  heavy  smoke,  consist- 
ing of  phosphoric  and  phosphorous  acids,  passing 
off  slowly,  allows  the  admission  of  only  a  small 
quantity  of  air.  Some  red  oxide  of  phosphorus  is 
also  deposited  on  the  upper  part  of  the  tube.  But 
the  combustion  becomes  at  once  more  vivid  by  in- 
clining the  tube,  and  when  the  tube  is  held  perpen- 
dicularly it  is  complete,  as  then  the  draught  of  air 
is  most  powerful.  In  this  way  phosphorus  may  be 
oxidized  to  either  degree  required ;  it  must  be  slowly 
burnt  to  form  phosphorous  acid,  imperfectly  to  form 
oxide  of  phosphorus,  and  completely  to  form  phos- 
12 


134  METALLOIDS. 

phoric  acid.      The  experiment  is  also  well  adapted  for 
illustrating  the  principle  of  draughts  in  chimneys,  &c 


14  1.  Phosphorus  was  formerly  obtained  from  urine, 
and  is  now  universally  prepared  from  bones.  Bones 
consist  of  gelatine,  lime,  and  phosphoric  acid  (P  O5). 

The  gelatine  is  removed  by  calcining  the  bones.  It 
is  burnt. 

The  lime  is  removed  by  sulphuric  acid.  Sulphate  of 
lime  is  formed. 

f  The  oxygen  (O5)  is  expelled  by  igniting 
Phosphoric  J      the  bones  with  charcoal  (carbonic  acid 
acid.  gas  is  disengaged). 

[  Phosphorus  (P)  remains  behind. 

As  phosphorus  is  volatile  and  highly  inflammable, 
the  phosphoric  acid  and  charcoal  are  heated  in  a  close 
vessel,  commonly  in  an  earthen  retort,  the  beak  of  which 
dips  under  water  contained  in  the  basin,  where  the 
vapor  of  phosphorus  is  to  be  condensed.  This  process 
is  accordingly  one  of  distillation.  The  carbonic  oxide, 
together  with  some  phosphuretted  hydrogen  and  car- 
buretted  hydrogen  gas,  escapes  through  the  water. 

Charcoal,  at  a  glowing  heat,  has  the  power  of  ab- 
stracting oxygen  from  almost  all  acids  and  bases,  as  in 
this  case  from  phosphorus,  or,  chemically  speaking,  to 
deoxidate  or  reduce  them  ;  thus  carbonic  oxide  (C  O), 
which  escapes,  is  formed  from  carbon  and  oxygen. 
Almost  all  metals  are  obtained  from  native  metallic 
oxides  or  ores,  by  heating  them  with  charcoal. 

PHOSPHURETTED  HYDROGEN  (P  H3). 

145.  Experiment.  —  Put  into  an  ounce  flask  a  quarter 
of  an  ounce  of  slaked  lime,  and  a  piece  of  phosphorus  the 
size  of  a  pea,  fill  it  up  to  the  neck  with  water,  and  place 


PHOSPHURETTED  HYDROGEN.  135 

it  in  a  small  vessel  containing  a  strong  solution  of  salt, 
prepared  by  adding  half  an  ounce  of  salt  to  an  ounce 
p.    83  and  a  half  of  water. 

Fit  to  the  flask  a 
bent  glass  tube,  one 
end  of  which  is 
made  to  dip  into 
a  basin  of  water ; 
heat  the  salt  water 
to  boiling,  and  a 
gas  will  be  evolved, 
which,  as  it  issues  from  the  tube  and  comes  in  contact 
with  the  air,  inflames  spontaneously.  This  gas  is  called 
phosphuretted  hydrogen,  and  consists  of  several  combi- 
nations of  phosphorus  and  hydrogen,  chiefly  of  P  Hs. 
If  you  collect  it  in  a  small  jar  filled  with  water,  it  im- 
mediately ignites  upon  the  admission  of  air.  Both  the 
phosphorus  and  the  hydrogen  combine  with  the  oxygen 
of  the  air,  and  there  results  phosphoric  acid  (P  O3)  and 
water  (3  H  O).  The  first  rises  as  a  white  smoke,  and 
the  gas,  as  it  issues  in  separate  bubbles  from  the  water, 
takes  the  form  of  a  wreath.  Phosphuretted  hydrogen, 
when  unburnt,  emits  the  smell  of  garlic. 

146.  In  the  preparation  of  sulphuretted  hydrogen 
(§  132),  the  iron  deprived  the  water  of  its  oxygen,  and 
the  sulphur  took  the  liberated  hydrogen.  What  these 
two  substances  together  accomplish,  phosphorus  can 
effect  alone ;  it  abstracts  from  the  water  both  its,  oxy- 
gen and  hydrogen,  and  it  divides  itself  between  the 
elements  of  the  water.  Phosphorus  forms  with  oxy- 
gon two  acids,  phosphoric  and  hypophosphorous  acids, 
which  remain  behind ;  but  it  forms  with  hydrogen  a 
volatile  gaseous  combination,  which  escapes.  Phos- 
phorus, however,  can  only  effect  this  in  the  presence  of 
a  strong  base,  for  instance,  lime,  with  which  the  acids 


136 


METALLOIDS. 


composed  of  phosphorus  and  oxygen  combine.  Thus, 
lime  d  jes  not  directly  aid  in  the  decomposition  of  water 
but  it  encourages  the  phosphorus  to  exert  more  powel 
and  activity.  The  lime  would  gladly  have  combined 
with  acids,  but  there  are  none  present ;  they  may,  how- 
ever, be  formed,  if  the  phosphorus  abstracts  the  oxygen 
from  the  water.  This  does  take  place,  and  we  can  say 
the  lime  urges  on  the  phosphorus,  —  disposes  it  to  de- 
compose the  water,  in  order,  as  it  were,  to  satisfy  its 
own  eagerness  to  unite  with  an  acid.  Thus  is  defined 
the  name  which  this  kind  of  affinity  has  received ;  it  is 
called  disposing  affinity.  This  term  expresses  an  affin- 
ity, an  eager  desire  to  combine  with  a  body  not  yet 
existing,  but  which  body  may  be  formed  from  the  ele- 
ments present,  and  which  is  in  reality  formed  in  conse- 
quence of  this  desire. 

147.  If  we  now  reflect  upon  the  processes  of  prepar- 
ing hydrogen  (§  84)  and  sulphuretted  hydrogen  (§  132), 
we  shall  see  that  in  both  of  these  instances  a  disposing 
affinity  is  also  exerted.      But  the  impelling  body,  in 
these  instances,  is   an  acid,  —  the  powerful   sulphuric 
acid.      This   acid   has  a   strong   desire  to  unite  with 
a  base,  and  it  urges  the  iron  to  convert  itself  into  a 
base,  which  is  readily  accomplished  when  the  iron  com- 
bines with  the  oxygen  of  the  water.     The  other  ele- 
ment of  the  water  is  thereby  set  free,  and  escapes  as  a 
gas,  in  the  first  case  alone,  in  the  second  accompanied 
by  sulphur,  which  the   iron   releases   at   the  moment 
when  it  combines  with  the  oxygen,  for  which  it  has  a 
preference. 

148.  It  may,  perhaps,  be  asked  why  the  sulphuric 
acid  did  not  immediately  combine  with  the  metallic 
iron,  or  the  lime  with  the  phosphorus ;  this  could  not 
take  place,  as  simple  substances,  with  but  few  exceptions, 
combine  only  with  simple  ones,  and  compound  only  with 


RETROSPECT  OF  THE  PYROGENS.         137 

Compound  substances.  Hence  the  compound,  sulphuric 
acid,  cannot  combine  with  the  simple  element,  iron,  but 
can  combine  with  the  compound,  protoxide  of  iron, 
Neither  can  the  compound,  lime,  enter  into  combination 
with  simple  phosphorus ;  but  it  will  do  so  immediately, 
when  phosphorus,  by  combining  with  oxygen,  becomes 
a  compound  body. 

149.  In  the  last  experiment,  the  flask  was  placed  in 
salt  water,  in  order  to  guard  against  the  ignition  of  the 
phosphorus,  in  case  the  flask  should  accidentally  break. 
Salt  water,  at  the  strength  specified,  will  not  boil  under 
109°  C. ;  consequently  the  boiling  in  the  flask  is  more 
active  than  if  it  had  been  placed  in  pure  water,  the 
temperature  of  which,  under  ordinary  pressure,  can 
only  be  raised  to  100°  C.  The  apparatus  for  heating 
substances  by  means  of  hot  water  or  saline  solutions, 
is  called  a  water  or  saline  bath.  By  such  contrivances 
extracts  are  evaporated,  and  substances  dried,  which,  at 
a  stronger  heat,  would  easily  burn,  or  be  otherwise  de- 
composed. 


Phosphorus  and  sulphur  are  especially  characterized 
by  then*  great  inflammability  ;  hence  they  may  be  called 
pyrogenS)  or  fire-generators. 


RETROSPECT  OF  THE  PYROGENS  (SULPHUR  AND 
PHOSPHORUS;. 

1.  Simple  bodies  combine  only  with  simple  bodies, 
compound  only  with  compound  bodies. 

2.  In  order  that  two  bodies  may  act  chemically  on 
each  other,  one  of  them  must,  as   a  general  rule,  be 
liquid  or  gaseous. 

12* 


138  METALLOIDS. 

3.  When  a  body  is  suddenly  precipitated  from  its 
liquid  or  gaseous  state,  as  a  solid,  it  is  then  obtained  as 
a  fine  dust  (milk  of  sulphur  and  flowers  of  sulphur). 

4.  All  finely  divided  and  porous  bodies  eagerly  ab- 
sorb gases,  and  condense  them  within  their  pores ;  in 
many  cases  this  is  done  so  powerfully  as  to  force  the 
gases   into   chemical   combination    (spongy   platinum, 
charcoal). 

5.  An  incomplete  combustion  or  oxidation  takes  place 
when  the  supply  of  air  is  deficient ;  ^a  slow  combustion, 
when  substances  combine  with  oxygen  at  the  common 
temperatures ;    but   a   complete  and  rapid  combustion, 
when  the  union  takes  place  at  a  high  temperature,  and 
with  an  abundant  and  constant  supply  of  air.     In  the 
two  former  cases,  lower  degrees  of  oxidation  are  formed, 
and  in  the  latter,  higher  degrees  of  oxidation. 

6.  In  chemical  reactions  the  right  of  the  strongest 
prevails;    a  stronger  chemical  substance  can  expel  a 
weaker  from  its  combination,  and  replace  it.     This  is 
called  decomposition  by  simple  elective  affinity. 

7.  Decomposition  by  double  affinity  takes  place  when 
two  combinations  mutually  exchange  elements. 

8.  If  a  single  or  double  elective  affinity  is  caused  by 
the  presence  of  a  third  body,  commonly  a  strong  acid  or 
a  strong  base,  it  is  called  disposing  affinity. 

9.  Deoxidate,  the  opposite  of  oxidate,  is  a  term  ap- 
plied to  the  depriving  compounds  of  their  oxygen. 

10.  In  order  to  detect  a  chemical  substance,  and  to 
separate  it  from  others,  the  solution  of  it  is  mixed  with 
reagents,  that  is,  with  such  bodies  as  form  with  it  an 
insoluble  compound  (precipitate),  or  change  its  color, 
smell,  (fee. ;  such  changes  are  called  reactions. 

11.  Taste  is  perceived  only  in  soluble  bodies,  odor 
only  in  volatile  ones. 


CHLORINE. 


139 


Fig.  84. 


THIRD   GROUP  OF  METALLOIDS:    HALOGENS. 

CHLORINE   (Cl). 
At.  Wt.  =  443.  —  Sp.  Gr.  =  2.5. 

'- 

150.  Experiment.  —  Pour  one  ounce  and  a  half  of 
muriatic  acid  upon  a  quarter  of  an  ounce  of  finely 
powdered  black  oxide  of  manganese,  and  heat  it  grad- 
ually in  a  flask,  to  which 
is  adapted  a  bent  glass 
tube ;  a  yellowish-green 
gas  is  disengaged,  which 
is  collected  by  a  process 
already  described.  This 
gas  is  called  chlorine 
(from  xXoopo'y,  green),  be- 
cause it  has  a  greenish 
color.  Fill  with  it  several 
six-ounce  bottles  of  white 
glass,  and  cork  them  up. 
Fill,  likewise,  a  bottle 

with  two  thirds  of  chlorine  and  one  third  of  water,  and 
shake  it  up ;  suction  is  exerted  upon  a  finger  which 
closes  the  mouth  of  it, —  a  proof  that  a  vacuum  has  been 
occasioned.  If  the  finger  be  removed,  the  air  rushes  in 
at  once.  This  vacuum  was ^  caused  by  the  chlorine 
having  been  dissolved  in  the  water,  which  may  be  in- 
ferred also  from  the  disappearance  of  the  yellow  color 
in  the  vacant  space  of  the  bottle.  One  measure  ot 
water  dissolves  two  measures  of  chlorine.  This  solu- 
tion is  called  chlorine  water. 

Muriatic  acid,  which  is  usually  prepared  from  com- 
mon salt,  is  a  combination  of  chlorine  and  .hydrogen, 
and  belongs  to  the  class  of  hydrogen  acids ;  if  it  be  de- 


2H  Cl— -^ 


140  METALLOIDS. 

prived  of  the  hydrogen,  the  chlorine  is  set  free.  This 
is  done  in  the  following  manner.  When  muriatic  acid 
is  added  to  hyperoxide  of  manganese  (Mn  (X),  the 
oxygen  of  the  manganese  takes  from  the  muriatic  acid 
its  hydrogen,  and  water  is  formed,  but  simultaneous- 
ly also  hyperchloride  of  manganese  (Mn  Ck),  from  the 
liberated  manganese  and  chlorine.  The  hyperchloride 
of  manganese,  however,  loses  at  a  very  gentle  heat  half 

of  its  chlorine,  just  as  the  oxy- 
Fiuid.  gen  escaped  from  the  hyper- 
oxide  of  manganese  at  a  glow- 
Fluid  'lnS  neatj  only  it  loses  it  far 
more  readily.  From  hyper- 
chloride of  manganese,  there  is  accordingly  formed  pro- 
tochloride  of  manganese  and  free  chlorine,  the  latter  of 
which  escapes  as  a  yellowish  gas.  Mn  Cl^  is  resolved 
into  Mn  Cl  and  Cl. 

If  the  oxygen  of  the  manganese  is  previously  expelled 
by  heat,  and  then  conducted  into  muriatic  acid,  it  no 
longer  possesses  the  power  of  withdrawing  from  the 
acid  its  hydrogen,  and  consequently  no  chlorine  will  be 
evolved.  Oxygen  has  this  power  only  at  the  very 
moment  when  it  is  separating  from  its  combination 
with  another  body,  that  is,  in  its  nascent  state.  When 
actually  liberated,  it  has  far  less  inclination  to  aban- 
don its  freedom.  This  .peculiarity  appertains  to  other 
elements,  and  it  is  often  taken  advantage  of  to  force 
into  combination  such  bodies  as  have  but  slight  affin- 
ity for  other  bodies,  and  which  combination  could  not 
have  been  effected  in  a  direct  way. 

Chlorine  is  not  only  obtained  from  manganese,  but 
from  all  bodies  which  part  easily  with  their  oxygen 
as,  for  instance,  chlorate  of  potassa,  red  lead,  &c.,  by 
heating  them  with  muriatic  acid. 


CHLORINE.  1 

151.  Muriatic  acid  derives  its  chlorine  from  common 
salt,  more  than  half  of  which  consists  of  chlorina;  con 
sequently,  this  gas  may  be  also  obtained  from  salt  by 
mixing  three  quarters  of  an  ounce  of  it  with   half  an 
ounce  of  black  oxide  of  manganese,  two  ounces  of  sul- 
phuric acid,  and  one  ounce  of  water,  and  heating  them; 
by  adding  sulphuric  acid  to  the   salt,  muriatic  acid  is 
formed,  and  set  free,  and  this  is   decomposed  by  man- 
ganese, in  the  way  already  mentioned. 

Chlorine  acts  as  a  poison  on  being  inhaled ;  hence, 
care  must  be  taken  not  to  inhale  it  while  operating  with 
it.  For  greater  security  pour  some  drops  of  alcohol  and 
ammonia  upon  a  cloth  and  wave  it  frequently  in  Ihe 
air ;  the  chlorine  contained  in  the  air  will  then  be  so 
altered,  that  it  will  lose  its  injurious  properties. 

152.  Experiments  with  Chlorine. 

Experiment  a.  —  In  order  to  recognize  the  odor  ot 
chlorine,  smell  cautiously  chlorine  water  (but  not  the 
gas) ;  the  chlorine  water  may  be  tasted  also  without 
danger.  The  smell  of  chlorine  is  peculiarly  pungent 
and  suffocating,  and  it  has  a  harsh,  styptic  taste. 

Experiment  b.  —  If  a  flask  containing  chlorine  gas  be 
exposed  to  the  air,  no  diminution  of  chlorine  will  be  per- 
ceptible ;  but  if  the  flask  be  inverted  it  will  contain  in  a 
short  time  only  atmospheric  air.  Chlorine  is  two  and 
a  half  times  heavier  than  common  air,  and  its  specific 
gravity  is  2.5. 

Experiment  c. —  Introduce  a  piece  of  litmus-paper  into 
chlorine  gas,  and  it  becomes  white ;  pour  chlorine  water 
upon  red  wine,  or  ink,  and  both  the  liquids  will  lose  their 
color.  Chlorine  bleaches  and  destroys  all  colors  derived 
from  the  animal  or  vegetable  kingdom.  In  consequence 
of  this  property,  chlorine  has  become  a  most  important 
agent  in  bleaching ;  and  linen,  cotton,  paper,  and  othei 


142  MKTAT.LOIDS. 

materials,  may  now  he  rendered  perfectly  white  by  it  in 
a  few  Jmurs;  while,  l>y  the  old  method  of  laying  them 
on  the  grass  in  I  he  sun,  weeks,  and  even  months,  were 
required  for  cllceting  it.  This  method  of  bleaching 
is  culled  quirk  bleaching,  the  other  is  called  »-w.vv- 
blraching.  The  modern  method  is  very  excellent,  and 
does  not  in  the  least,  injure  the  strength  of  the  fabric., 
provided  all  the  chlorine  be  completely  removed  again 
after  the  bleaching  is  finished,  which  is  not  so  easily 
done  as  many  bleachers  suppose,  If  this  precaution  is 
not  observed,  or  if  the  chlorine  water  is  too  strong  or 
in  excess,  then  indeed,  after  the  color  is  destroyed,  the 
fibres  of  the  yarn  or  fabric  itself  will  be  attacked.  The 
fault  is  not  to  be  attributed  to  the  chlorine,  but  rather 
to  the  injudicious  application  of  it.  A  salt  has  lately 
been  Introduced  into  commerce,  under  the  name  of 
antiehlorine,  by  means  of  which,  if  any  chlorine;  should 
happen  to  remain  in  the  bleached  materials,  they  will 
not  be  in  the  slightest  degree  injured  by  it.  As  the 
health  of  the  laborers  is  endangered  by  the  use  of  chlo- 
rine gas  or  chlorine  water,  chloride  of  lime  is  now 
substituted,  a  salt  in  which  chlorine  is  chemically  com- 
bined, but  from  which  it  may  be  easily  disengaged  on 
mere  exposure  to  the  air. 

Hr/H'rinienf.  d. —  Apply  chlorine  water  to  decaying 
and  nauseous  substances  (water  from  flower-pots,  ma- 
nure, rotten  eggs,  \re.) ;  the  bad  odor  will  at  once  en- 
tirely vanish.  Thus  it  not  only  decomposes  colors,  but 
also  the  volatile,  combinations  formed  during  decay,  and 
which  occasion  disagreeable  odors.  It  acts  in  a  similar 
manner  also  upon  morbific  matter  (malaria,  miasm), 
which,  being  diffused  in  the  air  or  attached  to  clothes 
and  beds,  may  communicate  disease.  Chlorine  is  there- 
fore a  powerful  disinfecting  agent,  and  is  used  for  puri 


CHLORINE.  143 

fying  all  morbid  matter  and  infected  atmospheres,  and 
for  arresting  the  decay  of  organic  substances.  ^  Musty 
casks  may  also  be  purified  by  washing  them  first  with 
chlorine  water,  and  then  with  some  milk  of  lime. 
Mouldy  cellars,  in  which  milk  or  beer  cannot  be  kept 
without  turning^sour,  are  again  rendered  serviceable  for 
a  long  time  by  fumigating  them  with  chlorine  gas,  or 
by  washing  them  with  chlorine  water,  or  a  solution  of 
chloride  of  lime. 

is.i-fx'riment  e.  —  Fill  a  small  flask  with  chlorine  wa- 
ter, and  invert  it  in  a  vessel  filled  with  water;  if  this  is 
put  away  in  a  dark  place,  it  remains  unchanged;  but  if 
it  is  exposed  to  the  sun,  a  colorless  gas  will  collect  in 
the  upper  part  of  the  flask,  in  which  a  glowing  taper 
will  inflame;  this  gas  is  oxygen.  After  some  days  the 
water  will  entirely  lose  its  chlorine  odor,  and  will  have 
acquired  a  sour  taste,  and  instead  of  bleaching  blue 
litmus-paper,  it  will  redden  it.  Three  elements  only 
were  present,  the  constituents  of  water  and  chlorine  ; 
thus  it  is  obvious,  that  the  chlorine  must  have  united 
w  i .  h  the  hydrogen  of  the  water  to  form  muriatic  acid,  the 
oxygen  being  set  free.  Chlorine  had  here  the  choice 

between     hydrogen    and 
oxygen  ;  it  chose  the  for- 
mer; it  has,  consequent- 
ly* a  greater  affinity  fc? 
hi/drugm  than  for  oxygen. 
This   affords  another  ex- 
ample of  simple  elective  affinity.     The  chlorine  water 
should  therefore  be  protected  from  the  light,  and  this 
can  be  most  conveniently  done  by  pasting  black  paper 
ound  the  vessel  containing  it. 

The  bleaching  and  disinfecting  power  of  chlorine  ig 
now  easily  explained  by  its  strong  affinity  for  hydrogen 


144  METALLOIDS. 

All  animal  and  vegetable  substances  contain  hydrogen 
which  is  taken  from  them  by  chlorine.     But  if  a  sin- 
gle chemical  pillar  falls,  the  whole  chemical  structure 
tumbles  with  it.     By  the  abstraction  of  the  hydrogen, 
the  coloring  matter  becomes  colorless,  the  odorous  prin 
ciples  scentless,  the  morbific  matter  innoxious,  insoluble 
substances  are  very  frequently  rendered  soluble,  &c. 
Experiment  f.  — Dissolve  in  a  test-tube  a  small  quan- 
tity of  green  vitriol  (sulphate  of 
Fl's-  &-  iron),  in  cold  water,  and  add  to 

the  solution  a  few  drops  of  sul- 


Remains  In 

solution. 


phuric  acid ;  then,  some  chlorine  water ;  the  solution  will 
immediately  assume  a  yellow  color.  In  this  case,  also, 
the  water  is  decomposed ;  the  hydrogen  passes  to  the 
chlorine,  but  the  oxygen  is  not  liberated,  since  it  here 
meets  with  a  body  which  already  contains  oxygen,  but 
which  is  capable  of  receiving  still  more,  namely,  protox- 
ide of  iron.  This  becomes  more  highly  oxidized,  and 
the  yellow  liquid  now  contains  sulphate  of  sesquioxide 
of  iron.  Consequently  we  have  in  chlorine  water  a 
powerful  oxidizing"  agent,  by  means  of  which  we  can 
easily  convert  protoxide  salts  into  salts  of  the  sesqui- 
oxide or  peroxide. 

Experiment  g.  —  Put  into  chlorine  water  some  pure 
gold-leaf ;  it  will  soon  disappear,  as  the  simple  element 
chlorine  combines  with  the  simple  element  gold.  The 
combination  is  called  chloride  of  gold ;  it  is  soluble  in 


CHLORINE.  145 

water.  Chlorine  has  a  very  great  tendency  to  combine 
with  the  metals.  These  combinations  comport  them- 
selves like  salts;  they  are  called  chlorine  metals,  and 
most  of  them  are  soluble  in  water. 

Experiment  h.^—  Pour  into  a  vessel  filled  with  chlo- 
rine gas  a  little  metallic  antimony,  in  fine  powder;  it 
will  fall  in  a  glowing  state  to  the  bottom,  as  though  it 
were  a  shower  of  fire.  The  fire  is  caused  by  the  violent 
combination  of  the  chlorine  with  the  antimony.  The 
white  smoke  which  fills  the  flask  is  the  new  combina- 
tion formed,  viz.  chloride  of  antimony.  If  a  fine  brass 
wire,'  on  which  a  piece  of  tinsel  has  been  fastened,  be 
introduced  into  chlorine  gas,  the  wire  will  burn  with  a 
vivid  combustion,  and  with  the  emission  of  sparks. 
Here  combustion  means  the  same  as  a  combination 
with  chlorine.  Brass  consists  of  zinc  and  copper;  ac- 
cordingly, chlorides  of  zinc  and  copper  are  formed. 
Both  dissolve  in  water,  and  the  chloride  of  copper  im- 
parts to  the  solution  a  green  tinge. 

Experiment  i.  —  Place  in  this  solution  a  polished 
knife-blade ;  in  a  short  time  it  will  be  covered  with  a 
coating  of  the  red  metal,  copper.  The  iron  possesses  a 
still  greater  affinity  for  chlorine  than  copper  does,  and,  as 
in  chemical  reactions  the  right  of  the  strongest  prevails, 
so  the  iron  seizes  the  chlorine,  and  the  copper  is  deposit- 
ed in  the  metallic  state.  This  method  is  frequently  em- 
ployed for  precipitating  a  metal  from  its  solution.  Pol- 
ished steel  is,  accordingly,  a  reagent  for  copper,  and  by 
means  of  it  we  can  ascertain,  very  simply  and  accurate- 
ly, whether  copper  is  present  in  pickled  cucumbers,  or 
preserved  fruit,  which  may  have  been  carelessly  prepared 
in  copper  vessels. 

153.  Experiment.  —  If  a  piece  of  sodium  of  the  size 
of  a  pea  is  thrown  into  a  cup  containing  chlorine  water, 
13 


.146  METALLOIDS 

it  will  move  rapidly  round,  just  as  in  common  water 
with  a  hissing  noise,  and  finally  disappear  ;  but  if  a  sut 
ficient  quantity  of  the  Chlorine  was  present,  the  liquid 
will  not  afterwards  give  a  basic  reaction,  as  in  the  ex- 
periment in  §67;  neither  will  it  have  an  alkaline,  but 
a  saline  taste.  If  allowed  to  evaporate  gradually  over 
a  warm  stove,  small  cubic  crystals  remain  behind,  the 
constituents  of  which  are  chlorine  and  sodium.  Thus, 
from  these  two  elements  a  salt  has  been  formed,  famil- 
iarly known  as  common  salt. 

154.  Chlorine,    like    oxygen   and    sulphur,    unites 
in  several  proportions  with  other  substances.     Thus, 
there    are    different    chlorides,    as    well    as    different 
oxides  and  sulphides.     The  combinations  containing 
smaller   quantities    of    chlorine   are   called   protochlo- 
rides;   those   containing  larger  quantities  are  called 
perchtorides. 

IODINE    (I). 
At.  Wt.  =  1586.  —  Sp.  Gr.  =  5. 

155.  Iodine  is  a  solid   body,  somewhat  resembling 
plumbago ;  it  smells  a  little  like  chlorine,  has  a  pungent 
taste,  and  stains  the  skin  brown. 

Experiment.  —  Put  24  grains  of  iodine  into  a  flask, 
and  pour  over  them  half  an  ounce  of  strong  alcohol ;  if 
the  iodine  is  pure  it  will  entirely  dissolve.  This  dark 
brown  solution  is  called  tincture  of  iodine.  Water  dis- 
solves only  a  trace  of  iodine,  but  yet  is  rendered  yellow 
by  it. 

Experiment.  —  Put  a  little  iodine  upon  a  knife,  and 
hold  it  over  the  flame  of  a  lamp ;  the  iodine  melts,  and 
is  afterwards  converted  into  a  violet-colored  gas,  —  io- 
dine fumes.  A.S  the  iodine  fumes  are  nearly  nine  times 


BROMINE, 

heavier  than  common  air,  they  sink  in  it.  Iodine  owes 
its  name  to  the  color  of  its  fumes,  the  Greek  word 
Iwdrjs  meaning  violet-colored.  The  fumes  appear  more 
beautiful  when  the  iodine  is  heated  in  a  small  flask. 
After  cooling,  the  walls  of  the  flask  become  lined  with 
small  brilliant  crystals  of  solid  iodine,  affording  an  ex- 
am pie  that  regular  crystals  may  also  be  formed  when 
bodies  pass  from  the  aeriform  into  the  solid  state. 

Experiment.  —  Boil  one  grain  of  starch  in  a  test-tube 
with  one  drachm  of  water,  and  add  to  the  thin  paste 
thus  obtained  a  few  drops  of  tincture  of  iodine;  the 
iodine  combines  with  the  starch ;  the  combination  is  of  a 
deep  blue  color.  The  blue  color  disappears  on  boiling, 
but  returns  again  on  cooling.  If  one  drop  of  the  starch 
paste  is  mixed  with  one  quart  of  water,  even  at  this  ex- 
treme dilution,  the  iodine  tincture  will  impart  to  it  a 
violet  tinge.  Consequently,  it  is  an  exceedingly  sen- 
sitive reagent  for  detecting  starch,  and  starch,  on  the 
other  hand,  for  detecting  iodine.  If  a  little  iodine  tinc- 
ture is  dropped  upon  flour,  potatoes,  &c.,  the  presence 
of  starch  in  these  substances  will  at  once  be  indicated. 

BROMINE    (Br). 
At.  Wt.  =  1000.  — Sp-  Gr.  =  3. 

156.  Bromine  is  a  deep  brownish-red,  heavy,  and 
very  volatile  liquid.  Its  name  is  derived  from  the  Greek 
word  pp&fjios,  signifying  a  strong  odor.  Bromine,  at 
common  temperatures,  emits  yellowish-red  fumes,  which 
have  a  suffocating  and  offensive  odor,  similar  to  that  of 
chlorine.  It  produces  a  yellow  color  with  starch. 

Iodine  and  bromine  have,  in  their  relations  to  other 
Dodies,  the  greatest  similarity  to  chlorine.  Like  chlorine, 
they  possess  a  strong  affinity  for  hydrogen,  and  form 


148 


METALLOIDS. 


with  it  acids ;  they  also  combine  with  the  metals  form- 
ing protoiodides  and  periodides,  protobromides  and 
perbromides,  which  comport  like  salts.  If  a  polished 
silver  plate  be  held  over  the  fumes  of  iodine  and  bro- 
mine, it  is  colored,  first  yellow,  then  violet,  and  then  blue> 
owing  to  these  vapors  combining  with  the  silver.  This 
film  of  iodide  and  bromide  of  silver  is  decomposed  al- 
most instantaneously  in  the  light,  slowly  in  the  shade, 
and  not  at  all  in  the  dark.  On  this  property  is  founded 
the  Daguerreotype  process.  Iodine  and  bromine  are 
also  used  in  medicine  for  dispelling  tumors  and  goitres, 
and  in  the  treatment-  of  scrofula,  &c. 

Both  of  these  two  substances  are  faithful  companions 
of  chlorine  ;  wherever  common  salt  occurs,  whether  in 
the  earth,  the  sea,  or  mineral  springs,  small  quantities 
of  them  are  present,  not^  in  a  free  state,  however,  but 
combined  with  metals.  The  different  sea-weeds  attract 
these  combinations  from  the  sea-water,  and  from  these 
sea-weeds  iodine  and  bromine  are  extracted.  Both  of 
these  bodies  have  poisonous  properties. 

FLUORINE  (Fl). 

At.  Wt.  =  235. 

Fluorine  is  likewise  an  element  having  similar  prop- 
erties to  chlorine,  but  it  is  hardly  known  in  its  isolated 
state.  The  mineral  known  as  fluor-spar,  crystallizing 
in  cubes,  consists  of  fluorine  and  calcium. 

CYANOGEN  (C2N  or  Cy). 
At.  Wt.  =  325.  —  Sp.  Gr.  =  1.8. 

157.  Prussian-blue )  universally  used  as  a  pigment,  con- 
sists of  iron,  carbon,  and  nitrogen.  But  both  the  two  lat- 


CYANOGEN.  149 

ter  substances  are  so  closely  combined  with  each  other, 
that  they  may  be  regarded  as  one.  The  most  striking 
thing  in  this  combination  is,  that,  although  a  com- 
pound, it  combines  with  other  elements  exactly  in  the 
same  manner  an  though  it  were  itself  an  element.  For 
this  reason,  under  the  name  cyanogen,  it  is  here  included 
among  the  elements.  It  forms  an  exception  to  the  pre- 
viously mentioned  rule,  that  simple  bodies  can  only 
combine  with  simple,  and  compound  only  with  com- 
pound bodies.  Cyanogen  comports  towards  other 
bodies  in  a  manner  similar  to  that  of  chlorine,  iodine, 
bromine,  and  fluorine;  it  is  gaseous,  and,  like  these, 
forms  with  hydrogen  an  acid,  the  poisonous  prussic 
acid,  and,  like  them,  also  unites  with  metals,  forming 
protocyanides  and  percyanides.  The  cyanogen  com- 
pounds have  likewise  the  character  of  salts.  The  com- 
bination of  cyanogen  with  iron,  as  already  stated,  is  of 
a  beautiful  blue  color,  and  hence  the  name  cyanogen, 
from  the  Greek  word  KVUVOS,  blue. 


The  five  metalloids,  chlorine,  iodine,  bromine,  flu- 
orine, and  cyanogen,  are  characterized  as  follows:  — 

1.  They  have  a  far  greater  affinity  for  hydrogen  than 
for  oxygen.      They   combine  with  the  latter  only  on 
compulsion  (oxygen  acids). 

2.  Their  combinations  with  hydrogen  are  acids  (hy- 
drogen acids). 

3.  Their   combinations   with   the   metals    are   salts 
These  salts  are  called  haloid  salts,  to  distinguish  them 
from  the  common  or  oxygen  salts,  which  consist  of  an 
acid  and  a  base. 

On  account  of  this  latter  peculiarity,  these  elements 
have  been  called  halogens,  or  salt  producers. 
13* 


150  METALLOIDS. 

RETROSPECT    OF    THE    HALOGENS    (CHLORINE,  IODINE 
BROMINE,  FLUORINE,  AND   CYANOGEN). 

1.  Crystals  may  be  formed,  —  1st,  from  a  solution, 
either  by  cooling  (saltpetre),  or  by  evaporation  (com 
mon   salt) ;    2d,   from  a  molten  fluid,   by  congelation 
(sulphur)  ;  and  3d,  from  vapor,  when  it  becomes  solid 
immediately  on  cooling  (snow,  iodine). 

2.  The  crystallized  or   regularly  formed   bodies   are 
the  reverse  of  the  amorphous  bodies,  in  which  no  defi- 
nite form  is  to  be  perceived  (vitreous  and  pulverulent 
bodies).     Many  bodies  can  assume  two,  or  even  several, 
different  forms,  and  are  called  dimorphous  or  polymor- 
phous bodies  (coal,  sulphur). 

3.  Water  can  dissolve,  not  only  solid,  but  gaseous 
bodies;   for  instance,  chlorine,  sulphuretted  hydrogen, 
&c.,  and  the  more  of  them  the  colder  it  is. 

4.  Not  only  heat,  but  light  also,  may  effect  or  de- 
stroy chemical  combinations. 

5.  A  body  has  a  greater  inclination  to  combine  with 
another  body  at  the  very  moment  when  it  is  separated 
from  a  combination  (nascent  state).   . 

6.  There  are,  also,  by  way  of  exception,  compound 
bodies,  which,  just  as  if  they  were  chemical  elements, 
can  combine  with  simple  bodies  (cyanogen). 

FOURTH  GROUP  OF  METALLOIDS:  HYALOGENS. 

BORON  (B), 
At.  Wt.  =  l36,and 

SILICON  (S).  * 

At.  Wt.  =  278. 

158.  Both  of  these  substances  occur,  in  nature,  only 
in  combination  with  oxygen ;  boron  but  seldom,  as  in 


RETROSPECT    OF    THE    METALLOIDS.  151 

boracic  acid  or  borax ;  and  silicon  very  abundantly 
as  in  sand,  quartz,  and  almost  all  other  stones.  The 
word  silicon  is  derived  from  the  Latin  silex,  flint ;  hence 
its  symbol.  Si.  Boracic  and  Silicic  acids  form,  with 
many  bases,  amorphous  salts  (glass,  slag,  glazing) ; 
for  this  reason,  boron  and  silicon  may  be  called  hyalo- 
gens  or  glass  producers. 


RETROSPECT    OF    THE    NON-METALLIC  BODIES,   OR 
METALLOIDS. 

1.  The  thirteen  substances  now  treated  of  may  be 
called  the  non-metallic  bodies,  or  metalloids,  because  they 
do  not  possess  a  metallic  appearance. 

2.  Heat  and  electricity  pass  through  them  very  slow- 
ly ;    they  are  bad   conductors   of  heat   and    electricity. 
The  metals,  on  the  contrary,  which  give  rapid  transit 
to  those  forces,  are  good  conductors. 

3.  On   decomposition  by  galvanism,  the  metalloids 
always  separate  at  the  positive  pole  (the  zinc  side),  and 
the  metals  at  the  negative  pole.     As  the  positive  pole 
only  attracts  bodies  endowed  with  the  opposite  or  neg- 
ative electricity,  and  the  negative  pole  only  those  en- 
dowed with  positive  electricity,  so  the  metalloids  are 
called   electro-negative  bodies   and  the  metals  electro- 
positive bodies. 

4.  Almost  all  the  metalloids   combine  with  hydro- 
gen, but,  as  a  general  rule,  the  metals  do  not.    Some  of 
the  hydrogen  combinations  have  acid  properties  (hydro- 
s&n  acids). 

5.  In  the  same  manner,  the  metalloids  combine  with 
oxygen,   forming    acid-oxides   or   oxygen   acids.      The 
metals  also  combine  with  oxygen,  but  forming  mostly 
oxides  or  bases. 


152  ACIDS. 

6.  The  following  are  the  states  of  aggregation  of  the 
metalloids  at  the  ordinary  temperature :  — 

7  metalloids,  solid :  C,  S,  P,  Se,  I,  B,  Si. 

1          "         fluid:  Br. 

5          «          gaseous:  O,  H,  N,  Cl,  (Cy). 

7.  They  form  four  families  or  groups,  founded  on 
their  resemblance  to  each  other. 

1st  group,  Organogens,  animal  and  plant  producers :  O, 

H,  N,  C. 

2d       u       Pyrogens,  fire  producers :  S,  P,  Se. 
3d       "       Halogens,  salt  producers:  Cl,  I,  Br,  F,  (Cy). 
4th      " '     Hyalogens,  glass  producers  :  B,  Si. 


ACIDS. 

FIRST   GROUP:   OXYGEN   ACIDS,   OR   COMBINATIONS  OF 
THE   METALLOIDS  WITH   OXYGEN. 

NITROGEN  AND  'OXYGEN. 

1.)  Nitric  acid,  or  aquafortis  (H  O,  N  O5). 
159.  Experiment.  —  Introduce  into  a  small  retort  half 
an  ounce  of  powdered  saltpetre  and  half  an  ounce  of 
common  sulphuric  acid,  and  let  the  retort  stand  erect 

for  some  time,  in 
order  that  as 
much  as  possible 
of  the  sulphuric 
acid  remaining 
in  the  neck  m% 
flow  down  into 
the  retort.  Then 
imbed  the  latter 


NITROGEN    AND    OXYGEN.  153 

in  sand  contained  in  an  iron  vessel,  adapt  to  the  beak  of 
it  a  receiver,  wrap  round  the  joint  some  strips  of  mois- 
tened blotting-paper,  and  heat  gently.  In  a  short  time 
a  yellowish  fuming  fluid  passes  over  into  the  receiver, 
which  is  placed  in  a  vessel  filled  with  water,  and  must 
frequently  be  sprinkled  with  cold  water ;  this  fluid  is 
heavier  than  water,  and  is  called  nitric  acid. 

Saltpetre,  is  a  salt,  consisting  of  nitric  acid  and  a 
base.  The  base  is  called  oxide  of  potassium,  or  more 
briefly  potassa,  and  has  for  its  symbol  K  O.  Sul- 
phuric acid  is  a  stronger  acid  than  nitric  acid ;  that 
is,  it  has  a  greater  affinity  than  the  latter  for  potassa ; 
it  therefore  expels  the  nitric  acid,  which,  by  the  appli- 
cation of  heat,  is  converted  into  vapor,  but  is  condensed 
again  in  the  receiver  as  a  fluid.  A  quarter  of  an  ounce  of 

sulphuric  acid  would  in- 
4-Voiatiie.  deed  have  been  sufficient 
to  expel  all  the  nitric  acid, 
volatile,  but  the  process  is  con- 
1  ducted  much  more  easily 

when  double  the  quantity  is  employed.  This  explains 
why  the  saline  residuum  left  in  the  retort  has  still  a 
very  acid  taste ;  it  is  called  fo'sulphate  of  potassa.  If 
only  one  half  of  the  sulphuric  acid  had  been  employed, 
neutral  sulphate  of  potassa  would  have  remained  be- 
hind. 

Nitric  acid  has  the  same  constituents  as  common  air, 
but  in  different  proportions.  The  air  contains  for  every 
four  measure?  of  nitrogen  one  measure  of  oxygen ;  nitric 
a^id,  on  the  contrary,  contains  ten  times  more  of  the 
latter  element;  consequently,  for  every  four  measures  of 
nitrogen,  ten  measures  of  oxygen ;  or,  what  is  the  same 
thing,  for  every  two  measures  of  N  (1  atom),  five  meas- 
ures of  O  (5  atoms).  These  two  gases  are  only  me 


154  ACIDS. 

chanically  mixed  together  in  the  air,  but  in  the  nitric 
acid,  on  the  contrary,  they  are  chemically  combined, 
This  is  a  striking  example  how  wonderfully  the  prop- 
erties of  bodies  change,  when  they  chemically  combine 
with  each  other.  When  mechanically  mixed  together, 
the  constituents  of  nitric  acid  form  a  life-sustaining 
gas,  while,  when  chemically  combined,  they  form  one 
of  the  most  corrosive  fluids. 

It  might,  perhaps,  be  supposed  that  nitric  acid  could 
be  formed  more  directly  and  simply  from  the  air ;  but 
this  cannot  be  done,  because  the  inert  nitrogen  will  not 
voluntarily  combine  with  oxygen  ;  this  combination 
can  only  be  effected  by  a  circuitous  method,  which  wiL 
be  described  hereafter. 

The  strongest  nitric  acid  contains  in  every  pound  two 
and  a  quarter  ounces  of  water,  or  in  each  atom  of  acid 
one  atom  of  water,  without  which  latter  it  cannot  exist ; 
if  this  is  withdrawn  from  it,  it  is  resolved  into  oxygen 
and  a  lower  oxygen-compound  of  nitrogen.  Many 
other  bodies,  especially  organic  bodies,  behave  in  a  sim- 
ilar manner.  This  water  has  been  called  water  of  con- 
stitution,  denoting  thereby  that  it  is  indispensably  neces- 
sary to  the  constitution — to  the  existence — of  the  bod- 
ies referred  to.  The  water  of  crystallization  is  neces- 
sary only  to  the  continuance  of  the  form  and  shape  of 
the  crystals.  The  crude  nitric  acid  of  commerce,  which 
is  commonly  prepared  in  large  iron  cylinders,  contains, 
perhaps,  from  10  to  12  ounces  of  water  in  the  pound ; 
consequently  it  is  three  or  four  times  weaker  than  the 
above. 

160.  Experiments  ivith  Nitric  Acid. 

Experiment  a.  —  A  drop  of  nitric  acid  is  sufficient  to 
acidify  several  spoonfuls  of  water,  and  even  at  a  greater 
dilution  it  will  redden  blue  litmus-paper ;  nitric  acid  is 
accordingly  distinctly  characterized  as  an  acid. 


NITROGEN    AND    OXYGEN.  155 

Experiment  b.  —  The  well-known  volatile  alkali,  more 
correctly  called  ammonia,  may  serve  as  the  antithesis  to 
the  acids.  It  has  an  alkaline  taste,  has  no  action  on 
blue  test-paper,  but  turns  red  test-paper  blue  ;  it  has  the 
character. of  a  base.  Its  exceedingly  pungent  odor  is 
also  characteristic. 

Experiment  c.  —  Add  carefully,  and  by  drops,  some 
nitric  acid  to  half  an  ounce  of  ammonia,  until  the  color 
of  red  or  blue  test-paper  remains  unchanged  by  it. 
When  this  point  is  attained,  you  will  no  longer  perceive 
either  the  acid  or  the  alkaline  taste  or  smell.  The 
taste  has  become  saline,  the  smell  has  vanished.  This 
process,  as  already  mentioned,  is  called  neutralization. 
Upon  evaporating  the  solution  a  white  salt  remains  be- 
hind, nitrate  of  Ammonia.  By  appropriate  means,  the 
nitric  acid,  as  well  as  the  ammonia,  may  be  again  liber- 
ated from  this  salt. 

It  is  characteristic  of  all  acids,  that  they  combine  with 
bases,  forming-  entirely  new  bodies,  called  salts,  and  thus 
lose  their  acid  properties. 

Experiment  d.  —  If  lead  be  heated  for  a  long  time  in 
the  air  it  abstracts  oxygen  from  it,  and  becomes  con- 
verted into  a  reddish-yellow  powder,  called  oxide  of  lead, 
or,  popularly,  litharge.  Take  up  a  small  portion  of  this 
litharge  on  the  point  of  a  knife,  put  it  into  a  test-tube, 
and  add  some  nitric  acid.  The  greater  part  will  be  dis- 
solved by  gentle  heating.  Filter  the  solution  while 
warm,  and  put  it  in  a  cold  place  ;  a  salt  will  be  depos 
ited  from  it  in  white  brilliant  crystals  of  nitrate  of  oxide 
of  lead.  This  shows  that  oxide  of  lead  is  also  a  base, 
as  it  combines  with  acids  forming  salts.  This  salt  is 
soluble  in  pure  water. 

Nitric  acid  dissolves  most  of  the  metallic  oxides,  and 
forms  with  them  salts,  all  >f  which  are  soluble  in 


156  ACIDS, 

water.  For  this  reason,  nitric  acid  is  often  used  fo? 
cleaning  metals,  for  instance,  copper  and  brass  instru- 
ments, which,  during  the  process  of  annealing,  solder- 
ing, &c.,  have  become  covered  with  a  coating  of  oxide. 

Experiment  e.  —  Pour  over  some  shot  common  nitric 
acid,  slightly  diluted  with  water ;  a  solution  is  also  ef- 
fected in  this  instance,  but  it  is  accompanied  by  the 
evolution  of  a  yellowish-red  vapor  of  a  suffocating 
smell.  This  vapor  is  called  nitrous  acid,  and  contains, 
as  its  name  implies,  less  oxygen  than  nitric  acid.  The 
missing  oxygen  has  united  with  the  lead,  and  has  con- 
verted it  into  an  oxide.  Part  of  the  nitric  acid  is  de- 
composed, while  another  part  of  it  combines  with  the 
oxide,  and  forms  the  same  salt,  as  in  the  former  experi- 
ment. This  likewise  crystallizes  from  jts  solution,  if  it 
is  evaporated  until  a  film  forms  on  its  surface. 

In  this  case  nitric  acid  exerts,  as  we  see,  a  double 
action ;  it  first  oxidizes  the  lead,  and  then  combines 
with  the  oxide  formed.  The  lead  is  apparently  dis- 
solved, but  it  is  obvious  that  this  is  quite  a  different 
kind  of  solution  from  that  of  common  salt  or  sugar  in 
water.  The  salt  and  sugar  are  unchanged  in  the  solu- 
tion, while  the  lead  is  not  contained  in  the  liquid  as  a 
metal,  but  as  a  salt,  a  nitrate.  The  same  thing  occur* 
with  all  other  metals  which  are  soluble  in  nitric  acid; 
as,  for  example,  with  silver,  mercury,  copper,  iron,  &c 
Gold  is  not  dissolved  by  it ;  hence  it  may  be  separatee* 
from  silver  by  means  of  nitric  acid. 

Experiment  /, —  The  metalloids,  as  well  as  the  met- 
als, are  oxidized  by  nitric  acid ;  charcoal,  on  being 
boiled  in  it,  becomes  carbonic  acid  ;  sulphur,  sulphuric 
acid  ;  phosphorus,  phosphoric  acid ;  &c.  In  all  these 
cases  yellowish-red  fumes  of  nitrous  acid  are  evolved. 

Experiment  g.  —  Organic  substances  also,  for  exam- 


NITROGEN    AND    OXYGEN.  157 

pie,  wool,  feathers,  wood,  indigo,  &c.,  are  oxidized  and 
decomposed  by  heating  with  nitric  acid.  This  sort  of 
decomposition  may  be  regarded  as  combustion  in  the 
moist  way.  If  organic  substances  are  allowed  to  re- 
main for  a  short  time  only  in  contact  with  this  acid, 
they  will  assume  a  yellow  color,  owing  to  the  evolution 
of  nitrous  acid.  In  this  manner  wood  may  be  stained, 
and  silk  may  be  died  yellow;  the  hands  and  clothes 
are  also  stained  yellow  by  nitric  acid.  Cotton  ex- 
periences a  most  remarkable  change  if  soaked  for  a 
short  time  in  the  strongest  nitric  acid;  it  will  then  de- 
tonate and  explode,  like  gunpowder,  only  far  more  vi- 
olently. (§  433.)  Strong  nitric  acid  is  partially  de- 
composed, and  colored  yellow,  by  the  rays  of  the  sun. 

If  you  color  some  water  blue  in  a  test-tube  with  one 
drop  of  solution  of  indigo  (§  173),  and  add  to  it  on  boil- 
ing one  drop  of  nitric  acid,  the  blue  color  will  disappear. 
This  behaviour  serves  for  the  detection  of  nitric  acid. 

Nitric  acid,  as  the  preceding  experiments  show,  is 
very  easily  decomposed,  and  with  the  liberation  of  oxygen, 
which,  in  the  nascent  state,  has  the  greatest  desire  to 
combine  again  with  other  bodies.  It  is,  owing  to  this 
property,  one  of  the  most  important  means  of  oxidation. 

Experiment  h.  —  The  nitric  acid  salts,  also,  are  easily 
decomposed.  Having  powdered  some  of  the  nitrate  of 
lead,  obtained  in  experiment  d  or  e,  throw  it  upon  a  red- 
hot  coal;  decomposition  \\;il  ensue,  with  the  emission 
of  sparks,  and  beads  of  metallic  lead  will  remain  be- 
hind. The  nitric  acid  will  hereby  be  completely  re- 
solved into  nitrogen  and  oxygen ;  the  latter,  as  well  as 
the  oxygen  of  the  oxide  of  lead,  combines  with  the  coal, 
forming  carbonic  aaid,  which,  together  with  the  nitrogen 
that  has  become  gaseous,  quickly  escapes  and  occasions 
the  emission  of  sparks.  This  sudden  evolution  of  gasea 
from  a  solid  body  is  called  detonation. 
14 


158  ACIDS. 

2.)  Nitrous  Add  (N  O3). 

161.  This  acid  is  always  produced  as  a  disagreeable 
secondary  product  from  nitric  acid,  when  this,  as  in  the 
previous  experiment,  is  employed  for  dissolving  or  ox- 
idizing metals  or  other  substances.      At  the  common 
temperature   it  forms  reddish-yellow  suffocating  fumes, 
which  at  a  very  low  temperature  may  be  condensed  into 
a  blue  liquid.     As  the  inhalation  of  these  vapors  is  in- 
jurious to  the  lungs,  experiments  performed  with  this 
acid  should  always  be  done  where  there  is  a  free  circu- 
lation of  air. 

Fuming  Nitric  Acid.  —  Nitric  acid  will  dissolve  large 
quantities  of  nitrous  acid  fumes,  and  is  thereby  con- 
verted into  a  reddish-yellow  liquid,  which  in  open  ves- 
sels gives  off  the  same  colored  fumes.  It  is  then  called 
fuming  nitric  acid  (N  O3  +  N  O5).  On  dilution  with 
water  it  becomes,  first  green,  then  blue,  and  finally 
colorless,  while  the  nitrous  acid  escapes. 

3.)  Nitric  Oxide  (N  OJ. 

162.  Experiment.  —  Pour  over  a   cent,  placed  in   a 
wide-mouthed  bottle,  a  little  water,  and  then  add  by 
degrees  some  nitric  acid,  until  a  brisk  effervescence  en- 
sues.   This  effervescence  is  caused  by  the  evolution  of  a 
gas,  which  must  be  collected  in  a  jar  of  white  glass 
over  the  pneumatic  trough.    It  is  called  nitric  oxide,  and 
consists  of  two*  measures  (1  at.)  of  nitrogen  and  two 

measures  (2  at.)  of  oxy- 
gen. Close  the  mouth  of 
the  jar  under  water;  it 
seems  to  be  empty,  for  the 
nitric  oxide  is  colorless ; 
but  if  the  jar  be  opened, 
and  air  be  carefully  blown 
in,  then  the  jar  becomes 


NITROGEN    AND    OXYGEN.  159 

filled  from  above  with  yellowish-red  vapors.  The  ni- 
tric oxide  takes  thereby  from  the  air  one  atom  of  oxy- 
gen, and  is  converted  into  nitrous  acid,  and  N  O2  be- 
comes N  O3.  On  account  of  this  property,  it  has  an 
important  application  in  the  preparation  of  common 
sulphuric  acid  (§  172).  It  is  here  formed  from  nitric 
acid,  because  the  copper  withdraws  from  it  three  atoms 
of  oxygen,  and  becomes  an  oxide,  which  combines  with 
undecomposed  nitric  acid,  forming  nitrate  of  the  oxide 
of  copper.  This  salt  is  obtained  in  blue  crystals  by 
evaporating  the  solution  of  the  cent. 

163.  4.)  Nitrous  Oxide  (N  O)  is  a  combination  of 
two  measures  (1  at.)  of  nitrogen  with  one  measure 
(1  at.)  of  oxygen ;  it  is  a  colorless  gas,  which,  when 
inhaled,  has  an  intoxicating  effect,  and  is  therefore 
called  also  exhilarating  gas.  This  gas  may  be  regarded 
as  /itmospheric  air,  containing  double  its  usual  amount 
of  oxygen. 


By  the  following  table  it  will  be  seen  that  both  the 
volumes  and  the  weights  of  the  constituents  of  the  four 
compounds  just  treated  of  are  in  regular  proportion :  — 

In  Weight.  In  Volume. 

oz.  oz. 

175  N.  with  500  0,  or  2  vols.  (1  at)  N.  with  5  vols.  (at.)  O,  to  N05. 

175  —     «     300  —  "2     "      (1  at.)  — •     "     3      u       "    —  «  N  Oa. 

175  —     «     200  —  "2     "      (1  at.)  —     «     2     "       «    —  "  N  Oa. 

175  —     "     100  —  "  2     "      (1  at.)  —     "     1     «       «    —  «  NO. 

By  one  measure  or  atom  of  oxygen  (O)  is  here  meant 
100  ounces,  grains,  &c.,  in  weight.  On  the  other  hand, 
by  two  measures  or  one  atom  of  nitrogen  (N)  is  meant 
a  quantity  in  weight  of  175  ounces,  grains,  &c. 


160 


ACIDS. 


CARBON  AND  OXYGEN. 

1.)    Carbonic  Acid,  or  fixed  air  (C  O.2) 
164.  It  has  already  been  shown,  when  treating  of 
carbon,  that  coal  and  all  our  combustible  substances 
form,  during  brisk  combustion,  carbonic  acid  (§  115), 
and  that  this  gas  may  be  detected  by  lime-water,  which 
is  thereby  rendered  turbid,  owing  to  the  formation  of 
an  insoluble  salt,  carbonate  of  lime.     Chalk,  limestone, 
and  marble  are  also  carbonates  of  lime,  and  from  them 
carbonic  acid  may  be  prepared  in  large  quantities. 
Experiment.  —  Pour  into  an  eight-ounce  flask  half  an 
Fig.  89.  ounce  of  nitric  acid  and 

half  an  ounce  of  water, 
and  then  add  some  pieces 
of  chalk  or  limestone. 
Adapt  to  the  flask  a  bent 
glass  tube,  and  conduct 
the  gas,  which  escapes 
with  effervescence,  into  a 
jar  placed  over  the  pneu- 
matic trough,  and  collect  it,  as  was  directed  under  oxy- 
gen. The  stronger  nitric  acid  expels  the  feebler  carbonic 

acid,  while  it  combines  with 
the  base,  lime  (Ca  O).  The 
nitrate  of  lime  formed  (Ca  O, 
N  O3)  is  a  soluble  salt ; 
therefore  there  remains  in 
the  flask  a  clear  liquid,  from  which,  by  evaporation, 
the  nitric  acid  salt  may  be  obtained  in  a  solid  form. 

Experiment.  —  Repeat  the  experiment,  but  instead  of 
nitric  acid  take  half  an  ounce  of  sulphuric  acid  (S  O3), 
carefully  diluted  with  two  ounces  of  water  (§  84) ;  you 
will  obtain  carbonic  acid  and  sulphate  of  lime.  The 


Volatile. 


CARBON    AND    OXYGEN. 


161 


liquid  in  this  case  does  not  become  clear,  since  the  sul- 
phate of  lime  (CaO,  SO,) 
volatile,  is  a  salt  difficult  to  dissolve ; 
it  is  the  same  substance 
with  that  commonly  called 
gypsum,  or  plaster  of  Paris. 
Having  finished  the  experiment,  collect  and  dry  the 
gypsum,  and  preserve  it  for  future  experiments.  The 
last  two  experiments  are  obvious  examples  of  simple 
elective  affinity. 

Experiment* — Add  some   sulphuric  acid  to  the  ni- 
tric acid  solution  of  the  first  experiment ;  the  clear  liquid 

will  become  thick  and  tur- 
bid, gypsum  being  likewise 
formed,   because    sulphuric 
acid,  which  is  stronger  than 
the   nitric  acid,  expels  the 
latter,  and  combines  with  the  lime. 
165.  Experiments  with  Carbonic  Acid. 
Experiment  a.  —  If  moistened  blue  test-paper  is  ex- 
posed to  carbonic  acid  it  is  reddened,  but  on  being  left 
in  the  air  for  some  time  the  blue  color  is  restored ;  car- 
bonic acid  is  a  volatile  acid. 

Experiment  b.  —  A  burning  taper  is  ex- 
tinguished when  held  in  carbonic  acid,  and 
it  is  fatal  to  men  and  animals  if  they  inhale 
it.  Carbonic  acid  gas  can  neither  support 
combustion  nor  life. 

Experiment  c.  —  Invert  a  jar  filled  with  car- 
bonic acid  over  one  containing  only  atmos- 
pheric air ;  if  after  some  moments  you  intro- 
duce into  each  of  these  jars  a  burning  taper, 
that  in  the  upper  vessel  will  continue  to 
burn,  while  that  in  the  lower  one  will  bo  ex* 
14* 


Fig.  90. 


162 


ACIDS. 


tinguished.  Carbonic  acid  is  heavier  than  common 
air  ;  it  has  sunk  into  the  lower  jar,  while  the  atmospheric 
air  has  ascended  into  the  upper  one.  If  a  flask,  filled 
with  carbonic  acid,  be  held  with  its  mouth  obliquely 
over  the  flame  of  a  lamp,  so  that  the  gas  can  flow  out, 
the  light  will  be  extinguished. 

Experiment  d. —  Repeat  the  experiment  of  the  two 
jars,  filling,  instead  of  the  upper  one,  the  lower  one  with 
carbonic  acid.  If,  after  some  hours,  you  add  lime-water 
to  both  of  the  jars,  and  shake  them,  you  will  obtain  in 
both  of  them  a  precipitate  of  carbonate  of  lime,  —  a 
proof  that  the  carbonic  acid  has  partly  ascended  into 
the  upper  jar.  Both  gases  have  intimately  united  to- 
gether, or  the  carbonic  acid,  though  heavier,  has  ascend- 
ed, and  the  common  air,  though  lighter,  has  diffused 
itself  towards  the  bottom.  This  voluntary  mixing  of 
the  different  kinds  of  gases  together  is  called  diffusion 
of  gases.  This  diffusion  of  gaseous  bodies,  since  it 
maintains  a  constant  equality  and  balance  of  the  con- 
stituents of  the  atmosphere,  is  of  great  importance  in 
the  economy  of  nature,  and  accounts  for  the  fact  tbat 
the  constitution  of  the  air  is  everywhere  nearly  uni- 
form, although  in  one  place  free  oxygen  is  withdrawn 
from  it,  and  in  another  place  carbonic  acid  is  added 
to  it 

Experiment  e.  —  Fill  a  flask  containing  carbonic  acid 
half  full  of  pure  water,  close  it  with  the  finger,  and 
shake  it ;  the  water  takes  up  the  carbonic  acid,  and,  as  a 
vacuum  is  formed,  the  finger  is  pressed  into  the  mouth 
of  the  flask  by  the  external  air.  Carbonic  acid  gas  is 
soluble  in  ivater ;  one  measure  of  it  will  dissolve  one 
measure  of  carbonic  acid,  but  twice  as  much  when  sub- 
jected to  pressure  ;  it  thereby  acquires  an  acid  taste,  and 
the  property  of  effervescing.  Such  waters  ooze  out 


CARBON    AND    OXYGEN.  163 

from  the  earth  in  many  places,  for  instance,  at  Setters 
and  Bilin,  and  they  are  used  for  their  medicinal  qual- 
ities, under  the  name  of  carbonated  waters.  They  are 
now  also  prepared  artificially.  From  this  it  appears 
that  carbonic  acid  is  innocent  when  taken  as  a  drink, 
but  is  injurious  when  inhaled.  The  foaming  of  bottled 
beer  and  champagne  is  owing  to  carbonic  acid,  formed 
during  the  fermentation  of  these  liquors,  and  kept  con- 
fined in  the  bottles  by  corking  them. 

Experiment  f.  —  Throw  a  Apiece  of  chalk  into  vinegar ; 
vinegar  is  one  of  the  weakest  acids,  yet  it  is  able  to 
expel  carbonic  acid  ;  this  escapes  with  effervescence. 
Carbonic  acid  is  a  very  feeble  acid,  because  it  has  a 
very  great  inclination  to  become  gaseous. 

Formerly  carbonic  acid  was  only  known  in  its  gas- 
eous state ;  but  in  recent  times  it  has  been  converted 
into  a  liquid,  by  a  strong  compressure  at  a  low  temper- 
ature. This  liquid  evaporates  with  such  great  rapidity, 
that  a  cold  of  nearly  — 100°  C.  is  produced  (§40)- 
By  this  means  chemists  have  lately  succeeded  in  ren- 
dering carbonic  acid  a  solid.  It  then  has  the  appear- 
ance of  snow  or  ice. 

166.  Experiment.  —  To  be '  perfectly  convinced   that 

carbon  is  contained  in  the 
colorless  carbonic  acid 
gas,  take  a  test-tube, 
break  the  bottom  of  it, 
and  adapt  to  it,  by  means 
of  a  perforated  cork,  a 
glass  tube,  and  connect 
it  with  a  flask  in  which 
carbonic  acid  is  evolved 

s^§  164).    Introduce  into  the  test-tube  a  piece  of  potassium 
of  the  size  of  a  pea,  previously  dried  between  blotting- 


164  ACIDS. 

paper,  and  heat  the  place  where  it  lies  with  a  lamp.  Po 
tassium  is  a  metal  very  similar  to  sodium,  and  has,  like 
that,  an  extraordinary  affinity  for  oxygen;  at  the  d2gree 
of  heat  produced  by  the  lamp,  it  is  enabled  to  withdraw 
the  oxygen  from  the  carbonic  acid  which  passes  over  it. 
This  takes  place,  and  oxide  of  potassium,  or,  more 
simply,  potassa  (K  O),  is  formed,  one  of  the  strong- 
est bases,  which  immediately  combines  with  a  portion 
of  the  acid  present,  forming  carbonate  of  potassa. 
This  is  colored  black  by  the  separation  of  carbon.  If 
you  put  the  test-tube,  containing  the  black  saline  mass, 
into  a  wide-mouthed  flask,  in  which  there  is  some  water, 
the  carbonate  of  potassa  will  dissolve,  but  the  carbon 
will  float  mechanically  in  the  solution,  and  may  be  col- 
lected on  a  filter.  The  liquid  has  a  basic  reaction,  since 
the  feeble  carbonic  acid  is  not  able  fully  to  neutralize 
the  alkaline  properties  of  so  strong  a  base  as  potassa. 
The  presence  of  carbonic  acid  is  proved  by  the  effer- 
vescence produced  on  the  addition  of  an  acid. 

Carbonic  acid  consists  of  one  atom  of  carbon  and 
two  atoms  of  oxygen,  and  has  consequently  the  formula 
C  O,,.  By  weight,  then,  75  ounces  or  grains  of  carbon 
are  united  with  200  ounces  or  grains  of  oxygen;  ac- 
cordingly, one  atom  of  carbon  is  equal  in  weight  to  75 
ounces,  grains,  &c.  of  carbon. 

167.  Carbonic  acid  is  everywhere  unceasingly  gener- 
ated, and  especially,  — 

a.)  In  those  regions  of  the  earth  where  volcanoes  are 
active,  or  probably  were  active  in  a  former  age.  It  is 
generated  at  the  Grotto  del  Cane,  near  Naples,  —  at  Pyr- 
mont,  in  Westphalia, —  and  in  the  neighbourhood  of  the 
Lake  of  Laache,  &c. ;  and  it  oozes  in  a  constant  cur- 
rent from  various  crevices  in  different  parts  of  the  earth. 

b.)  In  all  ordinary  combustion^  as  has  already  been 
mentioned  several  times 


CARBON    AND    OXYGEN.  165 

c.)  In  the  respiration  of  men  and  animals,  as  may 
easily  be  proved  by  blowing  the  air  coming  from  the 
lungs  through  a  glass  tube  into  lirne-water;  carbonate 
of  lime  is  formed,  which  renders  the  clear  liquid  turbid. 
We  inhale  oxygen ;  this  combines  in  our  bodies  with 
carbon,  and  is  again  exhaled  as  carbonic  acid  ;  there- 
fore, in  those  crowded  apartments  where  many  people 
congregate,  or  where  many  lights  are  burning,  some 
arrangement  should  be  made  by  which  the  vitiated  air, 
that  is,  air  rich  in  carbonic  acid,  may  be  conducted  off, 
and  be  replaced  by  fresh  air,  that  is,  air  rich  in  oxy- 
gen. This  is  accomplished  by  means  of  artificial  cur- 
rents of  air,  or  ventilation. 

d.)  In  the  fermentation  which  occurs  in  the  making  of 
wine,  beer,  and  brandy.  In  this  process  the  sugar  is  re- 
solved into  alcohol  and  carbonic  acid ;  the  former  re- 
mains in  the  liquor,  and  imparts  to  it  an  intoxicating 
power,  while  the  carbonic  acid  escapes  in  the  air. 

e.)  In  the  decay  and  putrefaction  of  all  animal  and 
vegetable  substances.  Carbon  is  contained  in  all  or- 
ganic bodies ;  during  decay  it  is  converted  gradually  by 
tlje  oxygen  of  the  air  into  carbonic  acid ;  hence,  wher- 
ever plants  and  animals  exist,  whether  upon  the  earth, 
in  the  sea,  or  in  the  air,  carbonic  acid  must  be  formed. 

All  the  carbonic  acid  thus  formed  is  received  into 
the  air.  If  it  should  continue  there,  however,  the  air 
would  become  gradually  deteriorated,  more  especially 
as,  in  all  the  processes  of  breathing,  combustion,  and 
decay,  free  oxygen  or  vital  air  is  taken  from  it.  But 
this  is  not  the  case.  The  oxygen  does  not  decrease. 
The  carbonic  acid  does  not  increase.  An  unfathom- 
able wisdom  has  appointed  the  vegetable  kingdom  as 
the  protector  of  animal  life,  and,  with  wonderful  sim- 
plicity, has  provided  that  plants  should  absorb  from  the 
air,  as  their  principal  means  of  support^  the  carbonic  acid 


166  ACIDS. 

Fj    ga  exhaled,  as  useless,  by  men 

and  animals,  and  should 
yield  oxygen  to  them  in 
return.    Plants  inhale  car- 
bonic  acid,  and    (during 
the  day)  exhale  oxygen. 
Lime-water  (§  115)  serves  for  the  detection  of  carbonic 
acid.     You  may  infer  the  presence  of  carbonic  acid  in 
solid  bodies,  if  an  effervescence  unattended  with  odor 
is  occasioned  by  dropping  muriatic  acid  upon  them. 
2.    Carbonic  Oxide  (CO)  has  already  been  treated  of. 

(§  no.) 

SULPHUR  AND  OXYGEN. 

1.)  Sulphuric  Acid  (S  O^). 

168.  What  iron  is  to  the  machinist,  sulphuric  acid  is 
to  the  chemist.  As  the  former  makes  out  of  iron,  not 
only  machinery  of  all  sorts,  but  also  instruments  by 
which  he  can  work  up  every  other  material,  so  sulphu- 
ric acid  has  also  for  us  a  double  interest.  It  not  only 
forms  with  the  bases  very  important  salts,  but  we  em- 
ploy it  also  as  the  most  useful  chemical  means  for  pro- 
ducing numerous  other  chemical  substances  and  changes, 
as  has  already  been  taught  in  the  preparation  of  hydro- 
gen, phosphorus,  chlorine,  nitric  acid,  carbonic  acid,  &c. 
Since  it  has  come  into  general  use  for  the  cleaning  of 
metallic  implements,  for  the  kindling  of  matches,  and  for 
making  blacking,  &c.,  it  is  well  known  as  a  sharp,  cor- 
rosive fluid.  It  stands,  as  it  were,  the  Hercules  among 
the  acids,  and  by  it  we  are  able  to  overpower  all  others, 
and  expel  them  from  their  combinations.  It  occurs  in 
commerce  as  a  liquid  only.  There  are  two  sorts ;  1)  an 
oily  fuming  liquid  (Nordhausen  sulphuric  acid,  or  oil  of 
vitriol) ;  and  2)  another  somewhat  thinner,  and  not 
fuming,  acid  (common  sulphuric  acid).  But  it  may 
V>e  obtained  in  a  solid  and  dry  state  in  the  following 


SULPHUR    AND    OXYGEN. 


167 


169    Anhydrous  Sulphuric  Acid. 

Experiment.  —  Pour  into  a  small  flask,  placed  in  a 
sand-bath  over  a  tripod  (see  Fig.  93),  half  an  ounce  of 
Nordhausen  sulphuric  acid,  and  heat  it  gently  till  it  boils 
moderately.'  Conduct  the  vapor  through  a  sufficiently 
wide  glass  tube  into  an  empty  flask,  which  is  placed  in 

Fig.  93. 


a  vessel  filled  with  cold  water.  In  summer  time  the 
water  may  easily  be  made  colder  by  adding  to  it  a  tea- 
spoonful  of  powdered  saltpetre.  If  the  vapor  be  suffered 
to  escape  into  the  air,  it  appears  in  thick  white  fumes, 
having  a  pungent  acid  smell ;  but  if  conducted  into  the 
flask,  it  is  condensed  into  a  glistening  white,  solid  mass. 
This  is  anhydrous  sulphuric  acid.  The  distillation 
stops  as  soon  as  the  boiling  ceases,  and  the  glass  tube 
becomes  so  hot  as  to  burn  the  hand.  What  remains  in 
the  flask  no  longer  fumes ;  it  has  become  common  sul- 
phuric acid.  To  cause  this  to  boil,  you  must  apply  a 
ten  times  stronger  heat  than  before,  for  it  does  not  be- 
gin to  boil  till  above  300°  C.,  while  the  anhydrous  acid 
boils  even  at  a  little  above  30°  C.  This  is  the 
why  the  boiling  ceases  when  the  latter  has  escaped. 


168 


ACID&. 


Experiments  with  Anhydrous  Sulphuric  Acid. 
Experiment  a.  —  Take  out  some  of  the  acid  by  means 
of  a  glass  rod,  and  introduce  it  into  a  dry  test-tube ;  it 
will  fume  violently,  and  after  a  time  become  fluid ;  that 
is,  it  attracts  water  from  the  air,  and  is  thereby  converted 
into  Nordhausen  sulphuric  acid.  On  longer  standing,  it 
absorbs  still  more  water,  and  ceases  to  fume ;  it  thus  be- 
comes common  sulphuric  acid.  By  evaporation  this 
water  cannot  again  be  removed,  for  the  sulphuric  acid 
will  deliver  this  up  only  when  we  present  to  it  a  base  in 
exchange. 

Experiment  b.  —  If  anhydrous  sulphuric  acid  be 
thrown  into  water,  it  is  dissolved  with  a  hissing  noise, 
and  a  violent  evolution  of  heat. 

Experiment  c.  —  It  is  likewise  dissolved  in  common 
sulphuric  acid,  converting  this  into  the  fuming  acid. 
Fuming  sulphuric  acid  is  accordingly  a  solution  of  an- 
hydrous in  common  sulphuric  acid.  Its  constituents 
are,  by  weight,  200  of  sulphur  (1  atom)  and  300  of  oxy- 
gen (3  atoms).  Hence  its  symbol  =  S  O3. 
170.  Fuming  Sulphuric  Acid. 

This  is  obtained  by  the  distillation  of  green  vitriol, 
which,  as  is  known,  consists  of  sulphuric  acid  and  pro- 
toxide of  iron.  (§  89.) 

Experiment.  —  Put  a  crystal  of  green  vitrio.  into  a 
glass  tube,  and  heat  it ;  aque- 
ous vapor  escapes,  and  the 
green  crystal  becomes  white 
(anhydrous).  On  further  heat- 
ing the  white  color  passes  into 
reddish-brown,  and  a  little  sul- 
phurous acid  is  evolved;  a  por- 
tion of  the  sulphuric  acid  gives 
up  one  atom  of  oxygen  to  the  protoxide  of  iron,  which 


SULPHUR    AND    OXYGEN.  169 

it  thus  converts  into  a  sesquioxide,  while  the  other  por 
tion  combines  with  the  oxide  of  iron.  If  this  basic  sul- 
phate of  sesquioxide  of  iron  be  strongly  and  continuously 
heated,  then  the  sesquioxide  of  iron  releases  the  sulphu- 
ric acid ;  and  tljis  escapes,  and  becomes  anhydrous,  be- 
<  ause  it  no  longer  finds  any  water  present.  In  prepar- 
ing it  on  a  large  scale  earthen  retorts  are  used,  and 
the  fumes  are  conducted  into  common  sulphuric  acid, 
which  is  thereby  converted  into  fuming  acid.  As  this 
is  a  thick,  flowing  liquid,  like  oil,  and  is  prepared  from 
green  vitriol,  it  has  received  the  name  of  oil  of  vitriol ;  it 
is  also  called  Nordhausen  sulphuric  acid,  because  thir. 
city  supplied  Germany  with  it  for  centuries.  Oil  of 
vitriol  has  the  specific  gravity  of  1.9,  and  contains  for 
every  pound  about  2  or  2|  ounces  of  water. 

If  oil  of  vitriol  be  exposed  to  the  air,  the  anhydrous 
acid  in  it  evaporates  and  unites  with  the  vapor  con- 
tained in  the  air;  accordingly,  common  sulphuric  acid 
is  formed,  which,  being  ten  times  less  volatile,  condenses 
in  the  cold  air,  forming  white  vapors,  just  as  steam  does. 
Consequently,  the  fumes  of  oil  of  vitriol  consist  of  the 
vapor  of  common  sulphuric  acid. 

As  long  as  the  process  of  manufacturing  sulphuric 
acid  from  green  vitriol  alone  was  known,  it  was  a  very 
expensive  article.  A  hundred-weight  is  now  obtained 
for  the  same  sum  that  was  formerly  paid  for  two 
pounds. 

171.   Common  Sulphuric  Acid  (H  O,  S  O3). 

Charcoal  and  phosphorus  on  burning  take  up  the 
greatest  quantity  of  oxygen  with  which  they  can  com- 
bine, and  we  obtain  carbonic  and  phosphoric  acids.  If 
sulphur  did  the  same,  nothing  would  be  easier  than  to 
convert  it  into  sulphuric  acid.  But  sulphur,  on  burn- 
ing, forms  sulphurous  acid  (S  O2),  that  is,  200  in 
15 


170 


ACIDS. 


weight  of  sulphur  (1  atom)  combines  with  200  in 
weight  of  oxygen  (2  atoms).  To  convert  this  into 
sulphuric  acid,  it  must  be  compelled  to  take  up  an- 
other 100  in  weight  of  oxygen  (1  atom).  This  is  done 
by  a  body  which  is  very  rich  in  oxygen,  and  which  like- 
wise readily  parts  with  it,  namely,  by  nitric  acid. 

Experiment.  —  Fasten  some  bits  of  sulphur  to  an  iron 
wire,  inflame  and  hold  them  in  a  capacious 
bottle  containing  a  little  water,  until  the 
blue  sulphurous  flame  is  extinguished ;  the 
bottle  becomes  filled  with  a  white  smoke, 
which  is  recognized  by  its  odor  as  sulphur- 
ous acid.  (§  64.)  If  you  now  introduce  a 
shaving  moistened  with  nitric  acid  into  the 
vessel,  reddish-yellow  fumes  will  immedi- 
ately form  around  the  wood,  gradually  filling  the  whole 
bottle.  These  fumes  are  nitrous  acid,  and  their  evolu- 
tion indicates  that  the  sulphurous  acid  has  withdrawn 
oxygen  from  the  nitric  acid,  and  has  been  oxidized  and 
converted  into  sulphuric  acid.  After  some  time  the 
flask  becomes  clear  again,  because  the  vapor  of  the  sul- 
phuric acid  formed  sinks  to  the  bottom,  and  dissolves  in 
the  water,  and  we  can  now  once  more  burn  sulphur  in 
the  bottle.  If  we  repeat  this  operation  several  times, 
we  can  soon  prepare  a  few  ounces  of  diluted  sulphuric 
acid. 

Experiment.  —  Add  some  drops  of  a  solution  of  a 
salt  of  barium  (chloride  of  barium)  to  a  portion  of  the 
acid  liquid  just  obtained  ;  a  strong  white  precipitate  is 
formed,  which  disappears  neither  by  boiling,  nor  by  the 
addition  of  water,  nor  by  nitric  acid.  This  precipitate 
is  sulphate  of  baryta^  a  salt  quite  insoluble  in  water  and 
acids.  Add  one  drop  of  the  diluted  acid  to  a  wineglass 
full  of  water,  and  add  to  this  a  solution  of  barium ;  even 


SULPHUR    AND    OXYGEN.  171 

at  this  great  dilution,  a  perceptible  cloudiness  will  be 
produced.  A  solution  of  chloride  of  barium,  or  of  ni- 
trate of  baryta,  are  the  most  certain  reagents  for  detect- 
ing sulphuric  acid  and  sulphates. 

172.  The  manufacture  of  common  sulphuric  acid  on  a 
large  scale  is  conducted  on  the  same  principle  as  in  the 
last  experiment  but  one.  The  sulphur  is  burnt  in  an 
oven,  from  which  a  pipe  leads  into  large  leaden  cham- 
bers. Vessels  containing  nitric  acid  are  placed  in  one 
of  the  chambers,  and  some  water  is  poured  upon  the 
floor.  The  sulphurous  acid  abstracts  one  atom  of  oxy- 
gen after  another  from  the  nitric  acid,  till  this  is  con- 
verted into  nitric  oxide.  The  nitric  oxide  formed  now 
acts  in  a  very  peculiar  manner.  It  has  been  stated 
(§  162)  that  this  gas  (N  02),  on  coming  in  contact  with 
the  air,  immediately  abstracts  from  it  one  atom  of  oxy- 
gen, forming  yellowish-red  fumes  of  nitrous  acid  (N  O3)  ; 
the  same  thing  takes  place  in  the  leaden  chambers,  since 
air  also  flows  into  the  chambers  at  the  ?ame  time  with 
the  sulphurous  acid.  The  nitrous  acid  willingly  gives 
up  again  this  one  atom  of  oxygen  to  bodies  which  have 
a  desire  for  it.  Such  a  body  is  sulphurous  acid.  Al- 
though it  is  too  inert  to  take  the  oxygen  directly  from 
the  air,  it  nevertheless  receives  the  oxygen  very  willingly 
when  it  is  presented  to  it  by  the  nitrous  acid.  Thus 
the  latter  becomes  again  converted  into  nitric  oxide,  but 
the  former  into  sulphuric  acid.  The  nitric  oxide  again 
takes  oxygen  from  the  air,  and  gives  it  up  again  to  the 
sulphurous  acid,  and  continues  to  perform  this  service 
as  long  as  any  oxygen  is  present.  Finally,  it  is  allowed 
to  escape,  together  with  the  remaining  nitrogen  of  the 
air.  But  it  is  essential  for  the  success  of  this  process, 
that  vapor  be  also  present ;  therefore  steam  is  continu 
ally  conducted  into  the  chambers  from  a  steam-boiler 


172  ACIDS. 

This  steam,  together  with  the  sulphuric  acid  formed, 
condenses  on  the  cold  walls,  and  collects  on  the  floors 
of  the  chambers  as  an  acid  liquid.  The  annexed  figure 
tends  to  elucidate  this  process. 


Fig.  98. 


4ir\ 

NO, 


By  means  of  this  remarkable  property  of  nitric  oxide, 
it  has  become  possible,  with  an  ounce  of  nitric  acid,  to* 
obtain  from  10  ounces  of  sulphur  30  ounces  of  concen- 
trated  common  sulphuric  acid.  If  the  three  atoms  oJ 
oxygen  released  from  the  nitric  acid  were  all  the  oxy 
gen  that  operated,  we  should  require  more  than  20 
ounces  of  nitric  acid  to  prepare  30  ounces  of  sulphuric 
acid.  There  are  now  some  laboratories  for  the  manu- 
facture of  sulphuric  acid,  of  such  colossal  size,  that  they 
are  able  to  deliver  daily  several  hundred  quintals  ol 
prepared  acid.  The  diluted  acid  formed  in  the  leaden 
chambers  requires  still  to  be  evaporated  down  nearly 
one  half,  in  order  to  convert  it  into  common  concentrated 
sulphuric  acid.  This  evaporation  is  commenced  in 
leaden  vessels,  and  finished  in  glass  or  platinum  re- 
torts. The  w^ater,  being  more  volatile,  escapes,  and 
carries  off  with  it  only  a  small  portion  of  the 


SULPHUR    AND    OXYGEN.  173 

When  the  specific  gravity  of  the  latter  becomes  1.84, 
that  is,  when  1840  grains  of  the  acid  can  be  put  into  a 
vessel  capable  of  containing  just  1000  grains  of  water, 
the  evaporation  is  stopped,  and  the  acid  is  transferred 
to  large  glass  battles,  or  carboys.  One  pound  of  com- 
mon sulphuric  acid  contains  three  ounces  of  water,  and 
consists  of  one  atom  of  acid  and  one  atom  of  water;  but 
this  atom  of  water  is  retained  so  firmly,  that  it  cannot 
be  expelled  by  any  heat.  This  acid  is  therefore  called, 
also,  hydrated  sulphuric  acid,  =  HO,  S  O3 . 

173.  Experiments  with  Sulphuric  Acid. 

Experiment  a.  —  Let  some  sulphuric  acid  remain  in 
an  open  flask  exposed  to  the  air ;  it  will  increase  every 
day  in  weight,  for  it  very  eagerly  attracts  water  from  the 
air.  After  standing  for  some  months  in  a  damp  place, 
it  will  become  two  or  three  times  heavier  than  before. 
This  explains  why  the  match-flasks  formerly  in  use  so 
readily  became  saturated  with  water.  Some  sub- 
stances impregnated  with  water,  especially  gases,  are 
drie.d  by  means  of  sulphuric  acid. 

Experiment  b.  —  A  piece  of  wood  introduced  into 
sulphuric  acid  becomes  black,  and  is  reduced  to  coal,  as 
if  it  had  been  exposed  to  the  flame  of  a  lamp.  The 
sulphuric  acid  seizes  upon  its  hydrogen  and  oxygen, 
which  combine  to  form  water,  and  the  carbon  is  left 
behind.  Wood  may  be  charred  in  this  way,  in  order  to 
protect  it  from  decay  in  moist  situations.  In  the  refin- 
ing of  burning-oil,  the  slime  of  the  oil  is  charred  by  sul- 
phuric acid.  Sulphuric  acid  chars  and  destroys  most 
vegetable  and  animal  substances. 

Experiment  c.  —  Pour  a  drop  of  oil  of  vitriol  upon 

paper ;  decomposition  takes  place  slowly ;  but  it  will 

take  place  instantaneously,  if  some  drops  of  water  are 

added,  because  water  and  sulphuric  acid  unite  together 

lr>* 


174  .  OIDS. 

with  the  evolution  of  strong-  heat.  For  this  reason,  wheia 
sulphuric  acid  comes  in  contact  with  the  skin,  it  should 
first  be  wiped  off  with  dry  paper  or  cloth,  and  then  be 
immediately  washed  with  a  great  quantity  of  water. 
If  50  measures  of  sulphuric  acid  are  mixed  with  50 
measures  of  water,  we  do  not  obtain  100  measures, 
but  only  97  measures,  of  liquid ;  consequently  a  con- 
traction or  condensation  has  occurred,  which  conden- 
sation is  always  attended  with  the  liberation  of  heat. 

Experiment  d.  —  Pulverize  a  small  quantity  of  indigo, 
and  form  a  thin  paste  of  it  with  fuming  sulphuric  acid. 
After  a  few  days  add  to  it  some  water,  and  you  obtain  a 
deep  blue  liquid,  —  solution  of  indigo.  With  this  solu- 
tion wool  may  be  dyed  of  a  fine  blue  color  (Saxon-blue). 
Common  sulphuric  acid  dissolves  indigo  only  imper- 
fectly. Indigo,  although  a  vegetable  substance,  is  not 
carbonized  by  sulphuric  acid,  thus  forming  an  exception 
to  the  general  rule. 

Experiment  e.  —  If,  during  the  winter  season,  you 
place  one  vessel  containing  fuming  sulphuric  acid,  and 
another  containing  the  common  acid,  in  a  cold  place, 
the  stronger  oil  of  vitriol  will  freeze  at  0°  C.,  but  the 
weaker  common  sulphuric  acid  will  not  freeze  until 
the  temperature  falls  to  — 34  3  C. 

Experiment  f.  —  Dissolve  half  an  ounce  of  the  soda 
of  the  shops  in  warm  water,  and  neutralize  with  dilute 
sulphuric  acid ;  evaporate  until  a  film  forms  over  the 
surface,  when,  on  cooling,  prismatic  crystals  will  be  de- 
posited ;  they  possess  a  bitter  saline  taste,  and  are  easily 
soluble  in  water.  The  common  soda  of  the  shops  is 
carbonate  of  soda  (Na  O,  C  CX)  ;  the  carbonic  acid  is 
displaced  by  the  stronger  sulphuric  acid,  and  escapes 
with  effervescence,  but  sulphate  of  soda  (Glauber  salts) 
remains  behind  in  the  liquid.  Almost  all  spring-water 


SULPHUR   AND    OXYGEN.  175 

contains  small  quantities  of  soluble  sulphates,  the  in- 
soluble or  almost  insoluble  sulphates  are  often  accu^ 
mulated  in  enormous  masses  in  nature,  forming  whole 
mountains,  as,  for  instance,  gypsum. 

Experiment  gv. —  Mix  to  a  thin  paste  half  an  ounce  of 
litharge  with  water,  and  add  gradually  a  quarter  of  an 
ounce  of  common  sulphuric  acid ;  after  a  while  a  white 
insoluble  body  is  formed.  The  acid  unites  with  the 
oxide,  forming  sulphate  of  the  oxide  of  lead ;  this  is  an 
insoluble  salt. 

Experiment  h.  —  To  half  an  ounce  of  copper  scales, 
such  as  fall  off  in  copper  founderies,  add  two  ounces  of 
water,  and  then  gradually  two  thirds  of  an  ounce  of 
sulphuric  acid,  and  put  it  in  a  warm  place;  you  obtain 
a  blue  solution,  from  which  afterwards  blue  oblique, 
rhomboidal  crystals  will  be  deposited.  The  edges  ot 
these  crystals  are  usually  obtuse,  giving  to  the  slender 
sides  a  roof-like  appearance.  Copper  scales  are  oxide 
of  copper;  and  they  combine  with  the  acid,  forming 
sulphate  of  oxide  of  copper  (blue  vitriol),  a  soluble  salt. 
By  the  designation  vitriol  is  always  to  be  understood 
a  sulphate  of  a  metallic  oxide.  Copper  or  iron  vessels 
are  cleaned  more  rapidly  and  made  brighter  by  water 
to  which  some  sulphuric  acid  has  been  added,  than  by 
simple  water  alone,  because  the  oxide,  which  tarnished 
the  vessels,  is  dissolved  by  the  acid. 

Experiment  i.  —  Put  a  small  iron  nail  into  a  test-tube, 
and  drench  it  with  20  drops  of  common  sulphuric  acid ; 
it  is  not  acted!  tepon.  But  if  you  add  a  little  water,  about 
four  or  five  times  more  than  the  acid,  a  brisk  efferves- 
cence will  ensue,  and  the  iron  will  be  dissolved.  The 
strong  acid  may  be  heated  to  boiling  in  iron  vessels 
without  acting  upon  them,  which  is  by  no  means  the 
case  with  the  diluted  acid.  It  has  been  stated  (§89) 


176 


ACIDS. 


that,  in  this  experiment,  hydrogen  escapes,  and  sul- 
phate of  iron  remains  in  solution.  The  iron  becomes 
protoxide  of  iron,  not  through  the  oxygen  of  the  acid, 
but  through  that  of  the  water.  Zinc  and  tin  comport 
themselves  in  the  same  manner.  Consequently,  dilated 
acid  must  be  employed  for  dissolving  such  metals. 
But  there  are  also  metals  which  dissolve  only  in 
stronger  acid,  for  instance,  copper,  silver,  &c. ;  this  will 
be  treated  of  more  fully  under  sulphurous  acid. 

Experiment  k.  —  If  a  meadow  or  field  be  irrigated 
with  one  pound  of  sulphuric  acid,  diluted  with  1000 
pounds  of  water,  the  soil  will  be  rendered  more  fertile 
and  productive.  The  reason  is,  that  the  sulphuric  acid 
decomposes  and  renders  soluble  several  kinds  of  earth ; 
whereby  soluble  sulphates  are  formed,  which  are  ab- 
sorbed by  the  plants,  and  accelerate  their  growth.  Sul- 
phuric acid,  if  only  100  times  diluted,  has  the  contrary 
effect,  and  may  serve  for  destroying  grass  and  weeds 
in  alleys,  &c. 

2.)   Sulphurous  Acid  (S  O.). 

174.  This  suffocating  gas  is  formed,  not  only  by  the 
combustion  of  sulphur,  but  may  also  be  prepared  from 
sulphuric  acid,  by  depriving  this  acid  of  one  atom  of 
oxygen. 

Experiment.  —  Put  into  a  flask  (see  Fig.  93)  half  an 
ounce  of  copper  filings,  and  two  ounces  of  common  sul- 
phuric acid,  and  conduct  the  gas  (S  CX),  as  it  escapes,  into 
a  four-ounce  bottle  filled  with  water  (for  the  precaution 
to  be  taken,  see  §  92) ;  the  gas  will  be  absorbed  by  the 
water  in  great  quantities,  and  will  impart  to  it  an  acid 
taste  and  a  suffocating  odor,  like  that  of  burning  sul- 
phur. One  measure  of  water  dissolves  about  forty 
measures  of  sulphurous  acid.  When  the  gas  ceases  to 
be  absorbed  by  the  water,  substitute  a  flask  filled  with 


SULPHUR    AND    OXYGEN.  177 

a  solution  of  carbonate  of  soda ;  this  likewise  absorbs 
the  gas,  and  forms  with  it  sulphite  of  soda,  while  the 
carbonic  acid  of  the  carbonate  of  soda  escapes.  After 
sufficient  evaporation,  the  salt  formed  will  shoot  out 
into  white,,  crystals,  now  known  in  commerce  by  the 
name  of  anti chlorine ;  it  is  able  to  bind  the  chlorine 
that  may  happen  to  remain  in  the  material  during  the 
bleaching,  and  to  render  it  harmless.  Sulphite  of  soda 
has  not  the  odor  of  sulphurous  acid,  unless  when 
drenched  with  diluted  sulphuric  acid,  which  combines 
with  the  soda,  and  expels  the  feebler  sulphurous  acid. 

Experiment.  —  Infuse  logwood  shavings  in  warm  wa- 
ter, and  pour  on  the  dark  liquid  thus  obtained  some  sul- 
phurous acid  water ;  a  decolorization  of  the  liquid  will 
immediately  take  place.  Sulphurous  acid  bleaches  veg- 
etable colors.  Straw,  wool,  silk,  and  catgut  —  indeed  ani- 
mal substances  especially  —  are  quite  generally  bleached 
with  sulphurous  acid.  The  most  simple  method  is  to 
moisten  them  with  water,  and  suspend  them  in  a  cham- 
ber or  in  a  box,  on  the  floor  of  which  is  placed  a  ves- 
sel containing  burning  sulphur.  The  bleaching  power 
of  this  acid  is  beautifully  exemplified  by  holding  a  rose 
or  a  peony  over  a  burning  stick  of  sulphur.  If  some 
drops  of  strong  sulphuric  acid  be  now  added  to  the 
bleached  infusion  of  logwood,  the  previous  dark  red 
color  will  again  be  restored;  consequently  the  coloring 
matter  has  not  been  completely  destroyed  by  the  sul- 
phurous acid,  as  it  would  have  been  by  chlorine ;  but  it 
has  only  combined  with  the  acid,  forming  a  colorless 
combination,  which  may  be  broken  up  again  by  a 
stronger  acid. 

Experiment.  —  If  a  lighted  taper  is  held  over  burning 
sulphur,  or  introduced  into  a  vessel  of  sulphurous  acid 
gas,  it  will  be  extinguished^  as  it  was  by  nitrogen  or  b^ 


178 


ACIDS. 


carbonic  acid.  The  continued  combustion  is  prevented, 
because  the  gas  contains  no  free  oxygen.  It  may  be 
now  readily  explained  how  chimneys  on  fire  are  extin 
guished  by  scattering  sulphur  on  the  coals  beneath  ;  the 
sulphurous  acid  gas  ascends  in  the  chimney,  and  ex- 
pels the  atmospheric  air  present  in  it ;  the  glowing  soot 
is  thereby  deprived  of  the  free  oxygen,  and  is  extin- 
guished. 

175.  It  now  remains  to  inquire,  what  has  become  of 
the  copper  and  the  sulphuric  acid,  from  which  the  sul- 
phurous acid  was  prepared. 

Experiment.  —  When  the  residue  in  the  flask  has  be- 
come cold,  add  water  to  it,  and  heat  it  gently  to  boiling, 
until  the  whole  saline  mass  is  dissolved.  The  solution 
is  dark  and  turbid,  because  fine  particles  of  coal,  con- 
tained in  almost  every  metal,  are  floating  about  in  it; 
but  after  filtering,  it  is  of  a  beautiful  blue  color,  and 
transparent.  If  allowed  to  cool  slowly,  blue  crystals  of 
sulphate  of  the  oxide  of  copper  (blue  vitriol),  of  con- 
siderable size,  are  formed ;  it  is  identical  with  the  salt 
obtained  by  the  solution  of  the  copper  scales  in  sul- 
phuric acid.  The  oxygen 
by  which  the  copper  was 
Volatile,  oxidized  proceeded  from 

the  sulphuric  acid,  half  of 
which  gave  up  an  atom 
Non.       of  oxygen,  and  was  there- 
voiatiie.     by  converted  into  sulphur- 
ous  acid,   but  the   other 

half  combined  with  the  oxide  of  copper  just  formed. 
If  copper,  like  iron,  could  be  oxidized  by  the  oxygen  of 
water,  then  one  ounce  of  sulphuric  acid,  instead  of  two 
ounces,  would  have  sufficed  for  half  an  ounce  of  copper 
Consequently,  in  preparing  blue  vitriol,  it  would  be 


so2 — -so2 

HO  SO,/ 
'       3X0 


PHOSPHORUS    AND    OXYGEN. 


179 


more  economical  previously  to  convert  the  copper  into 
an  oxide  by  heating  it  in  the  air,  and  then  dissolving  it 
in  sulphuric  acid.  Silver  and  mercury  comport  them- 
selves also  like  copper.  When  they  are  to  be  dissolved 
in  sulphuric-  acid,  concentrated  acid  must  be  used. 

When  larger  quantities  of  sulphurous  acid  are  re- 
quired, it  is  usually  pre- 
pared by  heating  sulphuric 
acid  with  charcoal.  Tl  e 
coal  likewise  abstracts  one 

Volatile.  . 

atom  of  oxygen  from  the 
sulphuric    acid,    and    be- 
comes converted  into  carbonic  oxide,  which  escapes  in 
company  with  the  sulphurous  acid. 


The  following  proportions,  in  weight,  of  sulphur  and 
oxygen,  always  exist  in  the  two  combinations  just  con- 
sidered :  — 

200  oz.  of  sulphur  and  300  oz.  of  oxygen,  or  1  at.  S  and  3  at.  0,  form  S  03. 
200   "  "  "    200   "  "         "1    "  S  and  2   "    O,     "     S  02. 

Sulphur  forms  with  oxygen  several  other  acid  com- 
binations, as  hyposulphuric  acid,  trithionic  acid,  hypo- 
sulphurous  acid,  tetrathionic  and  pentathionic  acids; 
but  these,  as  less  important,  will  not  be  treated  of  here. 

PHOSPHORUS  AND  OXYGEN. 

1.)   Phosphoric  Acid  (P  O5). 

176.  When  phosphorus  burns  with  a  flame  in  oxy- 
gen, or  in  the  air,  a  white  acid  vapor,  called  phosphoric 
acid  (§65),  is  formed ;  400  grains  of  phosphorus  are 
thereby  always  combined  with  500  grains  of  oxygen,  or 
1  atom  of  phosphorus  with  5  atoms  of  oxygen ;  this 


180 


ACIDS. 


acid,  consequently,  has  the  formula  P  Oa.  If  phos- 
phorus is  burned  under  a  dry  bell-glass,  this  vapor  will 
be  deposited  as  a  white  powder  (anhydrous  phosphoric 
acid),  which  diliquesces  in  the  air,  but  dissolves  in  wa- 
ter, for  phosphoric  acid  is  hygroscopic,  and  easily  solu- 
ble in  water.  Such  a  solution  may  also  be  obtained  by 
boiling  phosphorus  a  long  time  with  nitric  acid.  In  the 
preparation  of  it  by  combustion,  the  air  furnishes  the 
oxygen  ;  on  boiling  with  nitric  acid,  the  acid  itself  sup- 
plies it.  We  find  phosphoric  acid,  however,  already 
existing  in  many  substances,  especially  in  the  bones 
of  the  Mammalia  and  birds,  from  which  it  may  be 
prepared. 

Experiment.  —  Weigh  a  bone,  put  it  in  a  furnace-fire, 
and  let  it  remain  there  for  some  hours  ;  it  first  becomes 
black  and  then  again  white.  Now  take  it  from  the  fire 
and  again  weigh  it ;  it  has  lost  about  one  third  of  its 
weight.  That  which  was  lost  in  burning  was  gelatine, 
which  was  first  charred  by  the  heat  and  then  consumed, 
that  is,  converted  into  gas,  which  volatilized ;  the  re- 
maining non-volatile  parts  are  called  bone-ashes,  and 
consist  principally  of  phosphate  of  lime.  Reduce  this 
to  a  fine  powder.  Put  two  thirds  of  an  ounce  of  it  into 
a  flask,  and  add  to  it  half  an  ounce  of  sulphuric  acid 
and  four  ounces  of  water ;  let  it  stand  for  some  days  in 
a  warm  place,  occasionally  shaking  it.  Then  pour  the 
so:newhat  thick  mass  upon  a  cloth,  and  squeeze  out  the 
liquid.  This  contains  no  longer  sulphuric  acid,  but 
phosphoric  acid,  with  a  little  lime.  The  sulphuric  acid 
remains  on  the  cloth ;  it  has  combined  with  the  lime,  and 
expelled  the  phosphoric  acid.  The  sulphate  of  lime,  or 
gypsum,  (§  164,)  is  then  washed  with  water  and  dried. 

Sulphuric  acid  in  the  moist  way  is,  as  we  see,  stronger 
than  phosphoric  acid,  but  at  a  red  heat  the  contrary 


PHOSPHORUS    AND     OXYGEN  181 

is  the  case ;  if  gypsum  is  heated  to  redness  with 
phosphoric  acid,  the  sulphuric  acid  will  be  driven 
off,  so  extraordinary  are  the  changes  which  affinities 
experience  at  different  temperatures.  At  a  great  heat, 
the  least  volatile  acids  are  always  the  strongest ;  among 
these  belongs  phosphoric  acid,  since  it  does  not  volatil- 
ize until  it  attains  a  white  heat.  If  this  phosphoric  acid 
is  evaporated,  we  obtain  it  (still  containing  some  lime), 
first  as  a  sirupy  liquid,  and  finally  as  a  vitreous  solid  mass. 

To  detect  phosphoric  acid,  add  to  a  solution  of  it  some 
drops  of  nitrate  of  silver  and  ammonia ;  a  yellow  precipi- 
tate is  produced  (phosphate  of  the  oxide  of  silver).  But 
if  the  acid  had  been  previously  ignited,  the  precipitate 
would  have  been  white ;  consequently,  the  properties  of 
phosphorus  are  partially  changed  by  strong  ignition.  A 
more  accurate  test  consists  in  adding  to  the  liquid  under 
examination  a  few  drops  of  a  solution  of  Epsom  salts 
and  ammonia ;  if  phosphoric  acid  is  present,  a  crystal- 
line precipitate  (§  251)  is  formed. 

The  body  of  an  adult  man  contains  about 
from  9  to  12    pounds  of  bones,  containing 

"     6  "     8    pounds  of  bone  ashes,  containing 

"     5  "     7    pounds  of  phosphate  of  lime,  containing 

"    2J  "     3    pounds  of  phosphoric  acid,  containing 

"     1  "     1}  pounds  of  phosphorus. 

Phosphates  are  also  contained  in  the  blood,  flesh,  and 
other  portions  of  the  body.  Whence  does  it  obtain  this 
phosphorus  ?  Answer ;  from  the  meat  and  vegetables 
which  it  consumes.  The  phosphate  salts  occur  in  bread, 
in  all  kinds  of  grain,  in  leguminous  and  many  other 
plants,  particularly  in  their  seeds.  But  how  do  the 
plants  obtain  these  salts  ?  By  means  of  the  soil.  If 
arable  land  contained  no  such  salts,  no  seeds  could  be 
produced.  If  we  increase  their  quantity  by  mixing 
bone-ashes  with  the  soil,  we  place  the  latter  in  a  situa- 
16 


182  ACIDS. 

tion  to  produce  a  larger  quantity  of  grain  ;  consequent- 
ly, bones  furnish  us  with  a  powerful  manure.     Thai 
the  gelatine  contained   in  them  contributes   also  to  the 
growth  of  plants,  will  be  treated  of  hereafter. 
2.)   Phosphorous  Acid  (P  O3). 

177.  This  acid,  which  contains  for  one  atom  of  phos 
phorus  only  three  atoms  of  oxygen,  is  formed  princi 
pally  when   phosphorus  is  slowly  burnt,  that  is,  when 
without  being  heated  it  takes  up  oxygen  from  the  air, 
as  was  shown  in  §  140. 

3.)  A  combination  of  equal  atoms  of  phosphorus  and 
oxygen  is  called  hypophosphorous  acid. 

4.)  Oxide  of  Phosphorus  (P2O).  The  red  substance 
formed  during  the  imperfect  combustion  of  phosphorus 
(§§  142,  143)  contains  even  less  oxygen  than  hypophos- 
phorous acid,  and  is  oxide  of  phosphorus  (mixed  with 
red  phosphorus,  §  139). 

In  phosphoric  acid  (P  O5),  400  ounces  of  phosphorus 
are  always  combined  with  500  ounces  of  oxygen,  or  1 
atom  P  with  5  atoms  O;  in  phosphorous  acid  (P  O3), 
400  ounces  of  phosphorus  are  always  combined  with 
300  ounces  of  oxygen,  or  1  atom  P  with  3  atoms  O. 

CHLORINE  AND  OXYGEN. 

178.  Chlorine  has  but  a  feeble  affinity  for  oxygen, 
and  may  be  combined  with  it  only  in  an  indirect  way, 
and  with  the  assistance  of  strong  bases,  which  immedi- 
ately unite  with  the  acids  produced,  forming  salts. 

1.)  Hypochlorous  acid  is  a  combination  of  two  meas- 
ures or  one  atom  of  chlorine  with  one  atom  of  oxygen 
(Cl  O),  and  it  is  characterized  by  its  power  of  destrpy- 
ing  all  vegetable  colors.  It  is  resolved  with  great  ease 
into  free  chlorine  and  oxygen.  It  is  the  bleaching1  prin- 
ciple of  the  well-known  chloride  of  lime. 

2.)    Chloric  acid  consists  of  one  atom  of  chlorine  and 


CYANOGEN  AND  OXYGEN. 

five  atoms  of  oxygen ;  thus  its  formula  is  Cl  O5.  As  it 
is  so  rich  in  oxygen,  and  releases  it  very  readily  when 
heated,  its  salts  are  frequently  employed  for  obtaining 
oxygen,  or  for  combining  other  substances  with  oxygen 
(oxidizing  them).  The  salt  of  this  kind  most  commonly 
employed  is  the  chlorate  of  potassa,  which  was  used  in 
some  of  the  earlier  experiments. 

3.)  Perchloric  acid  is  a  combination  of  one  atom  of 
chlorine  and  seven  atoms  of  oxygen. 

Bromine  and  iodine  comport  themselves  like  chlorine, 
and  combine  with  oxygen,  forming  acids,  which  are 
easily  decomposed.  Fluorine  does  not  unite  at  all  with 
oxygen. 

f 

CYANOGEN  AND   OXYGEN. 

179.  Cyanogen,  although  composed  of  two  elements 
(carbon  and  nitrogen),  comports  itself,  nevertheless,  ex- 
actly like  a  simple  body,  and,  moreover,  like  a  salt-former, 
and  can  form  several  acids  with  oxygen.  Two  of  these 
are  of  great  interest  in  a  scientific  point  of  view,  because 
they  have  quite  the  same  constitution,  but  entirely  dif- 
ferent properties.  They  consist  of  equal  atoms  of 
cyanogen  and  oxygen.  One  of  them  is  called  fulminic 
acia  (Cy2  O2),  and  is  united  with  the  oxide  of  mercury  in 
fulminating  mercury,  and  with  the  oxide  of  silver  in  the 
fulminate  of  silver.  The  well-known  percussion-caps 
afford  a  familiar  example  of  the  violence  with  which 
these  salts  explode,  on  being  rubbed  or  struck  by  some 
hard  body.  One  of  these  caps  contains  only  one  third 
of  a  grain  of  fulminate  of  mercury.  The  fulminic  acid 
separates,  on  exploding,  into  two  gases,  nitrogen  and 
carbonic  oxide,  which  suddenly  occupy  a  space  several 
thousand  times  greater  than  before.  The  second  acid 


184 


ACIDS. 


is  called  cyanic  acid  (CyO);  it  likewise  decomposes 
very  readily,  but  without  explosion  or  danger. 

Bodies  which  contain  just  the  same  constituents,  and 
in  exactly  the  same  quantity,  but  at  the  same  time  are 
quite  dissimilar  in  their  properties,  are  called  isomeric 
(from  la-os ,  equal)  and  /ie'/w,  part),  or  similarly  constituted 
bodies. 

BORON  AND  OXYGEN. 

Boracic  Acid,  BO3. 

180.  Experiment.  —  Dissolve  in  a  porcelain  dish  half 
an  ounce  of  borax  in  an  ounce  and  a  half  of  boiling 
water,  and  add  muriatic  acid  by  drops  to  the  solution, 
until  the  liquid  gives  a  strong  acid  reaction ;  on  grad- 
ually cooling,  the  boracic  acid  will  separate  in  scaly 
plates,  which  are  purified  by  being 
again  dissolved  and  recrystallized. 
Boracic  acid  is  combined  in  borax 
with  a  base,   soda ;   the   stronger 
muriatic  acid  seizes  upon  this  soda, 
and  forms  with  it  muriate  of  soda 
(or  chloride  of  sodium  and  water), 
which  remains  dissolved,  while  the 

less  soluble  boracic  acid  separates  from  the  liquid  in  crys- 
tals. There  are  some  places  in  Italy  where  hot  vapors 
containing  boracic  acid  issue  from  the  earth ;  large  quan- 
tities of  this  acid  are  now  obtained  from  these  vapors, 
by  conducting  them  into  basins  of  water,  where  they 
condense  with  the  boracic  acid. 

Experiment.  —  Take  a  piece  of  small  platinum  wire, 
about  two  and  a  half  inches  long,  and  bend  one  end  of 
it  into  a  hook ;  moisten  this  part  with  the  tongue  and 
dip  it  into  boracic  acid,  so  that  a  small  portion  of  it  may 


BORON    AND    OXYGEN.  185 

remain  adhering  to  the  platinum.  Now  direct  with  the 
lips  a  stream  of  air  through  the  blow-pipe  into  the  flame 
of  a  spirit-lamp,  and  approach  the  boracic  acid  to  the 
point  of  the  horizontal  flame ; 
it  will  first  melt  and  swell  in 
its  water  of  crystallization  into 
a  spongy  mass,  but  by  contin- 
uous blowing  will  be  converted 
into  a  transparent  glass  bead. 
Boracic  acid  does  not  volatilize 
on  ignition.  If  you  moisten 
the  glass  bead,  and  apply  to  it, 
either  powdered  chalk,  litharge, 
or  iron-rust,  and  again  heat  it  to 

melting,  these  substances  will  unite  most  intimately  with 
the  boracic  acid,  and  be  dissolved  by  it,  and  likewise 
vitrified.  Most  of  the  combinations  of  boracic  acids 
with  bases  become  vitreous  on  heating ;  that  is,  they 
melt  together,  forming  sometimes  a  white,  and  some- 
times a  colored  glass. 

181.  The  blow-pipe  is  an  excellent  instrument,  on  a 
small  scale,  for  volatilizing,  heating  to  redness,  melting, 
oxidizing,  or  reducing  substances.  A  double  combus- 
tion takes  place  in  the  blow-pipe  flame,  in  the  interior 
by  means  of  the  air  which  is  blown  into  it,  and  exter- 
nally by  means  of  the  atmospheric  air.  By  this  means, 
two  cones  of  light  are  formed,  a  smaller  interior  cone,  of  a 
blue  color,  and  a  larger  exterior  cone,  of  a  yellowish  ap- 
pearance ;  the  former  is  called  the  reducing  flame,  the  lat- 
ter the  oxidizing  flame.  If  you  wish  to  take  oxygen  from 
a  body,  —  for  instance,  from  an  oxide,  —  hold  it  at  the 
point  of  the  blue  interior  flame,  where  it  meets  with  soot 
or  carbon,  which  combines  with  the  oxygen  of  the  oxide, 
forming  carbonic  acid.  But  if,  on  the  other  hand,  a 
16* 


186  ACIDS. 

body  is  to  be  oxidized,  then  it  is  held  at  the  point  of 
the  outer  flame,  where  the  oxygen  of  the  air  can  have 
free  access  to  it.  In  order  to  acquire  a  practical  knowl- 
edge of  the  blow-pipe,  first  attempt  to  convert  a  piece  of 
lead,  placed  upon  charcoal,  into  an  oxide,  by  exposing 
it  to  the  outer  flame ;  ard  afterwards  to  restore  this 
oxide  to  its  original  metallic  state,  by  exposing  it  to 
the  inner  flame,  in  order  to  reduce  it.  The  habit  must, 
moreover,  be  acquired,  of  breathing  through  the  nose 
while  blowing,  and  to  do  this  the  cheeks  must  be  kept 
constantly  distended.  When  this  habit  is  acquired, 
the  chest  is  no  longer  strained  by  blowing,  and  a  long 
uninterrupted  stream  of  air  may  be  kept  up. 

182.  Experiment.  —  If  you  mix  some  boracic  acid  in 
a  mortar  with  alcohol,  and  kindle  the  latter,  it  will  bum 
with  a  green  flame.  In  this  way  boracic  acid  may  easi- 
ly be  detected.  Some  of  the  acid,  though  not  volatilized 
by  heat,  as  shown  in  a  previous  experiment,  escapes  with 
the  alcohol.  Other  bodies  also  exhibit  a  similar  incon- 
sistency ;  when  heated  by  themselves,  they  are  complete- 
ly non-volatile,  but  they  volatilize,  and  frequently  at  very 
low  temperatures,  when  they  find  themselves  in  company 
with  another  body  which  is  very  volatile.  Thus,  in  the 
present  instance,  the  alcohol  is  the  occasion  of  the  vola- 
tilization of  the  boracic  acid.  Hot  steam  will  also  ren- 
der large  quantities  of  non-volatile  silicic  acid  volatile, 
and  carry  it  off  with  itself.  Common  salt  is  constantly 
taken  up  by  the  vapors  which  rise  from  the  ocean  into 
the  air;  it  is  again  precipitated  with  the  rain,  and  in 
t]us  manner  is  diffused  over  the  whole  earth. 

Boracic,  like  phosphoric  acid,  is,  in  the  moist  condi- 
tion, a  very  weak  acid,  but  at  a  glowing  heat  it  is  one 
of  the  strongest  acids. 


SILICON    AND    OXYGEN.  187 


SILICON  AND  OXYGEN 

Silicic  Acid,  or  Silica  (Si  O.). 

183.  That  which  is  commonly  called  flint  is  cabled 
in  chemistry  silicic  acid.      We  find   it  tolera- 
Fig.  99.     j-jjy  pure  jn  quartz  an j  fljn^  and  in  rock   crys- 
tal often    beautifully   crystallized   in   six-sided 
prisms,  or  six-sided  pyramids,  and  so  transpar- 
ent, that  ornamental  stones,  the  so-called  Bo- 
hemian diamonds,  are  made  from  it.     The  red 
cornelian,  the  violet  amethyst,  the  green  chrys- 
oprase,  the  variegated  agate    and  jasper,  the 
opal  and  chalcedony,  —  these  well-known  pre- 
cious stones  consist,  likewise,  of  silica ;  their  colors  are 
chiefly  owing  to  the  presence  of  metallic  oxides.     Com- 
mon sand  is  rendered,  by  hydrated  oxide  of  iron  (rust), 
yellow  or  brown  colored  silica.    In  its  natural  state,  silica 
is  so  hard  as  to  give  sparks  with  steel,  and  is  quite  in- 
soluble in  water  and  acids,  except  hydrofluoric  acid.     It 
may,  perhaps,  seem  astonishing  to  some,  that  such  bodies 
as  our  common  sand,  or  flint,  should  be  included  among 
the  acids.     The  reason  is,  that  silica,  just  like  other 
acids,  combines  with  bases,  and  forms  salts.    . 

Experiment.  —  Boil  in  a  porcelain  vessel  one  drachm 
of  finely  ground  sand  and  two  drachms  of  caustic 
alkali,  with  one  ounce  of  water,  for  some  hours,  sup- 
plying the  water,  occasionally,  as  it  evaporates;  then 
let  the  mixture  stand  in  a  closed  vessel,  for  the  impu- 
rities to  settle.  Part  of  the  sand  dissolves  in  the  alkali, 
and  forms  with  it  a  thickish  opalescent  mass.  If  you 
add  muriatic  acid  to  this  solution,  a  thick  gelatinous 
precipitate  of  silicic  acid  will  be  formed.  If,  on  the 
contrary,  you  previously  dilute  the  liquid  with  from  ten 
to  twelve  times  its  quantity  of  water,  and  then  remove 


188  ACIDS. 

the  potassa  by  muriatic  acid,  the  liquid  will  remain 
clear,  and  the  silicic  acid  remain  dissolved  in  the  water. 
But  this  solubility  is  destroyed  as  soon  as  the  solution 
is  evaporated  to  dry  ness,  and  the  silicic  acid  is  then 
thrown  down  as  a  white  powder,  which  is  completely  in- 
soluble in  water.  Thus,  as  is  obvious,  silicic  acid  exists 
also  in  two  quite  dissimilar  isomeric  modifications,  one 
insoluble,  as  occurring  in  siliceous  stones  and  rocks ;  and 
another  soluble,  as  found  in  plants  and  water. 

Almost  all  our  springs,  as  well  as  our  plants,  contain 
small  quantities  of  silicic  acid.  If  we  evaporate  spring- 
water,  we  find  silica  in  the  insoluble  residuum ;  and  if 
we  burn  a  plant,  we  obtain  it  in  the  ashes.  Grasses, 
and  the  different  sorts  of  grain,  are  particularly  rich  in 
silica,  and  for  this  reason  they  have  been  called  siliceous 
plants.  Silica  is  to  these  plants  what  bones  are  to  men, 
—  the  substance  to  which  the  stalk  owes  its  firmness 
and  stiffness.  If  the  soil  is  deficient  in  soluble  silica,  (or 
if  there  is  not  enough  potassa,  which  renders  the  silica 
soluble,)  these  properties  will  be  wanting  to  the  stalk, 
and  it  will  bend  over.  The  horse-tail  plant  (Equise- 
tum)  contains  so  much  silica  that  it  may  be  used  for 
polishing  wood.  Silicic  acid  is  found  even  in  the 
animal  kingdom,  particularly  in  the  class  of  Infusoria?, 
which  are  only  visible  under  the  microscope ;  the  shells 
of  many  Infusoria?  are  formed  of  silicic  acid. 

The  combination  of  silicic  acid  with  bases  may  be 
effected  more  com,,  etely  by  fusion.  Most  of  the  sili- 
cates thus  obtained  are  amorphous,  and  are  said  to  be 
vitreous.  Silicic  acid  has  in  this  respect  the  greatest 
resemblance  to  boracic  acid,  and  it  also  resembles  it  in 
being  an  extremely  feeble  acid  in  its  moist  state ;  but 
when  heated,  on  account  of  its  non-volatility,  it  sur- 
passes all  other  acids  in  strength.  In  its  isolated  state, 


RETROSPECT    OF    THE    OXYGEN    ACIDS.  18!» 

silicic  acid  can  be  melted  only  by  the  heat  of  tho  oxy 
hydrogen  blow-pipe. 


RETROSPECT  OF  THE  OXYGEN  ACIDS. 

1.  Most  of  the  combinations  of  the  metalloids,  01 
non-metallic    elements,  with  oxygen,   are    acids    (acid 
oxides). 

2.  Most  of  the  combinations  of  the  metals  with  oxy- 
gen are  bases  (basic  oxides). 

3.  The  acids  redden  blue  test-paper,  the  bases  color 
the  red  paper  blue  (when  they  are  soluble). 

4.  The  acids  have  an  acid  taste,  and  the  bases  an 
aUailitie  taste  (when  they  are  soluble). 

5.  When  acids  and  bases  combine  together,  the  acid 
as  well  as  basic  properties  are  destroyed  (neutraliza- 
tion), and   new  compounds   are   formed,   salts;    these 
have  a  brackish  taste  if  soluble  in  water,  but  are  taste- 
less if  insoluble  in  water. 

6.  The  principal  characteristic  of  the  acids  is,  that 
they  combine  ivith   bases,  forming   salts;   therefore  we 
class   all  bodies  which  do  this  among  the  acids,  even 
if  they  do  not  possess  an  acid  taste  or  reaction.     The 
same  rule  applies  conversely  to  the  bases. 

7.  Most  of  the  acids,  in  the  state  in  which  they  are 
commonly  obtained  and  employed,  are  chemically  com- 
oined  with  a  fixed  quantity  of  water  (hydrates).    Many 
acids  cannot  exist  without  water  (water  of  constitu- 
tion).    By  adding  more  water,  we  obtain  the  diluted 
acid. 

8.  One  and  the  same  element  often  forms  several 
acids,  with  unequal,  but   always   fixed,  quantities  of 
oxygen. 

9.  The  acids   have  an  unequal    affinity   for   bases ; 


190 


ACIDS. 


some  have  a  greater  affinity,  for  example,  sulphuric 
acid ;  others  a  less,  as  carbonic  acid  ;  the  former  is  called 
a  strong,  the  latter  a  feeble  acid.  Feeble  acids  may 
be  expelled  from  their  combinations  by  the  stronger 
ones. 

10.  The  non-volatile  acids  are,  when  heated  (in  their 
dry  condition),  mostly  stronger,  but  at  ordinary  tem- 
peratures (in  the  moist  condition)  weaker,  than  the  vol- 
atile acids.     The  strength  of  the  affinity  consequently 
varies  according  to  the  temperature. 

11.  The  acids  just  considered  are  called  in  a  narrow 
sense  oxygen  acids,  because  they  contain  oxygen,  and 
owe  to  it  their  acid  properties. 

12.  The  combinations  of  oxygen  acids  with  bases  are 
Called  oxy-salts. 


SECOND   GROUP:  HYDR  ACIDS,  OR   COMBINATIONS   OF 
THE  HALOGENS  WITH  HYDROGEN. 

184.  As  oxygen  combines  with  the  metalloids,  form- 
ing acids,  so  also  hydrogen  can  convert  some  of  them 
into  acids.  The  Jive  halogens  —  chlorine,  bromine,  io- 
dine, fluorine,  and  cyanogen  —  are  acidified  by  hydrogen. 
Oxygen,  as  has  been  shown,  is  able  to  form  several 
acids  with  one  and  the  same  metalloid;  for  instance, 
with  sulphur  it  forms  sulphuric  and  sulphurous  acids; 
with  nitrogen,  nitric  and  nitrous  acids,  &c. ;  but  hydro- 
gen produces,  with  each  of  the  above-named  halogens, 
only  a  single  acid  or  combination. 


CHLORINE  AND  HYDROGEN,  MURIATIC  ACID   (II  Cl). 

185.  Experiment.  —  Put  into  a  porcelain  capsule  a 
grain  or  two  of  common  salt,  and  drench  it  with  sul- 


CHLORINE    AND    HYDROGEN. 


191 


phuric  acid ;  there  escapes,  with  effervescence,  a  gas, 
which*"  has  a  pungent  odor,  an  acid  taste,  and  reddens 
moistened  blue  test-paper ;  this  gas  is  muriatic  acid,  or 
hydrochloric  acid.  If  you  pour  some  ammonia  upon 
a  shaving,'  and  wgve  the  latter  to  and  fro  over  the  cap- 
sule, a  thick  white  smoke  is  formed;  and  the  acid 
odor  of  the  muriatic  acid,  and  also  the  pungent  fumes 
of  the  ammonia,  vanish.  The  acid  fumes  are  neu- 
tralized by  the  volatile  base  contained  in  the  ammonia  ; 
there  is  formed  an  odorless  salt  (chloride  of  ammonium), 
and  in  such  a  minute  state  of  subdivision,  that  it  floats 
in  the  air.  We  can,  in  this  way,  easily  determine 
whether  the  air  contains  muriatic  acid,  or,  by  reversing 
the  experiment,  whether  it  contains  ammonia,  and  also 
deprive  these  gases  of  their  suffocating  and  injurious 
properties,  and  remove  them  from  the  air. 

Experiment.  —  Mix  carefully  in   a  flask  a  quarter  of 
an  ounce  of  water  with  three  quarters  of  an  ounce  of 

Fig.  100. 


sulphuric  acid,  and  after  the  mixture  has  become  cold, 
add  to  it  half  an  ounce  of  common  salt.  Adapt  to  the 
neck  of  the  flask  a  cork  provided  with  a  glass  tube, 
the  long  limb  of  which  passes  into  a  phial,  containing 


192 


ACIDS. 


one  ounce  of  water.  If  you  heat  the  flask  in  a  sand- 
bath,  the  muriatic  acid  escapes,  but  more  quietly  than  in 
the  former  experiment,  because  the  sulphuric  acid  has 
been  somewhat  diluted.  The  tube  must  but  just  dip 
into  the  water  ;  for  should  it  reach  to  the  bottom  of  the 
phial,  the  whole  liquid  might  suddenly  flow  back  into 
the  flask,  if  the  heat  should  chance  to  slacken,  as  it 
might,  for  instance,  from  the  flickering  of  the  spirit-lamp 
by  an  accidental  current  of  air.  The  muriatic  acid  is  so 
eagerly  absorbed  by  the  water,  that,  when  the  evolution 
of  the  gas  diminishes,  a  vacuum  is  formed  in  the  tube 
and  flask ;  the  exterior  air  then  presses  more  strongly 
upon  the  water  and  forces  it  up  (§  92).  When  a  gase- 
ous body  condenses  into  a  liquid,  it  no  longer  requires 
the  latent  heat  by  which  it  became  gas  or  vapor,  and 
therefore  this  heat  is  set  free.  From  this  it  follows  that 
the  water  in  which  the  muriatic  acid  condenses  or  dis- 
solves must  soon  become  warm.  But  warm  water  can 
receive  much  less  gas  than  cold ;  accordingly,  in  order  to 
obtain  a  concentrated  solution  of  muriatic  acid  gas,  we 
must  place  the  phial  in  a  basin  of  cold  water.  When 
the  liquid  in  the  receiver  has  sufficiently  increased,  one 
of  the  blocks  must  be  withdrawn  from  beneath,  so  as 
to  keep  the  end  of  the  tube  near  the  surface  of  the 
liquid.  The  solution  thus  obtained  has  an  intensely 
acid  taste  and  reaction ;  it  is  called  hydrochloric  acid, 
but  is  commonly  known  under  the  name  of  muriatic 
acidi  One  measure  of  water  absorbs  more  than  four 
hundred  measures  of  muriatic  acid  gas ;  the  strong  mu- 
riatic acid  thus  obtained  fumes  in  the  air,  because  a 
part  of  the  gas  escapes.  If  you  heat  it  to  boiling 
then  half  of  it  escapes,  and  an  acid  only  half  as  strong 
remains  behind ;  but  this  is  always  somewhat  heavier 
Mian  water. 


CHLORINE    AND    HYDROGEN. 


193 


The  muriatic  acid  of  commerce  is  commonly  yellow, 
and  contaminated  with  sulphurous  acid,  sulphuric  acid, 
chlorine,  iron,  and  sometimes  even  with  arsenic.  Muri- 
atic acid  is  likewise  manufactured  from  common  salt 
and  sulphuric  acid ;  but,  instead  of  glass  vessels,  large 
iron  cylinders  are  employed,  capable  of  containing  some 
quintals  of  common  salt.  The  gas  is  conducted  into 
several  bottles  or  jars,  connected  with  each  other,  and 
which  are  filled  with  water.  When  the  water  in  the  first 
vessel  becomes  saturated  with  hydrochloric  acid,  the  gas 
passes  over  into  the  second,  then  into  the  third  vessel, 
and  so  on,  saturating  each  successively.  This  is  a  very 

convenient  method 
of  conducting  gas- 
es through  liquids. 
Such  vessels,  which 
are  commonly  pro- 
vided with  two  or 
three  necks,  are  call- 
ed Woulfe's  bottles. 
The  upright  tube  in 
the  middle  neck  serves  as  a  safety  tube,  that  is,  it  pre- 
vents the  liquid  from  being  forced  back ;  if  a  vacuum  is 
formed  in  one  of  the  bottles,  the  air  enters  through 
this  tube. 

Common  salt  consists  of  chlorine  and  sodium  ;  if 
water  is  added  to  it,  the  chlorine  will  abstract  from  it 
hydrogen,  and  the  sodium  oxygen,  and  muriate  of  soda 

is   formed.     This  is   de- 
Voiatiie.     composed    by  the  more 
powerful  sulphuric  acid, 
which  combines  with  the 
base,  and  expels  the  hy- 
drochloric acid.     The  sulphate  of  soda  (Glauber  salts) 
17 


194  ACIDS. 

remains  behind  as  a  white  salt,. and  is  used  in  the  man- 
ufacture of  the  important  article,  carbonate  of  soda. 

The  constituents  of  muriatic  acid  gas  are  equal 
atoms  of  chlorine  and  hydrogen,  and  it  is  represented 
by  the  symbol  H  Cl. 

If  you  fill  a  jar  half  with  chlorine  and  half  with  hy- 
drogen, and  put  it  in  a  dark  place,  no  union  ensues, 
but  it  takes  place  instantaneously  when  the  jar  is  ex- 
posed to  the  direct  rays  of  the  sun.  The  union  is  ac- 
companied by  a  violent  detonation,  which  often  breaks 
the  glass,  so  that  it  is  not  advisable  to  perform  this  ex- 
periment. But  it  proves  that  light  also  compels  some 
substances  to  combine  chemically  with  each  other. 

186.  Experiments  with  Muriatic  Acid. 

Experiment  a.  —  Put  some  iron  nails  in  a  phial,  and 
pour  upon  them  some  muriatic  acid ;  brisk  effervescence 
will  ensue.  When  this  has  continued  some  minutes, 
hold  a  burning  taper  over  the  mouth  of  the  phial ;  the 
gas  which  escapes  inflames ;  it  is  hydrogen.  The  mu- 
riatic acid  is  decomposed,  and  its  second  constituent, 
chlorine,  combines  with  the  iron.  The  iron  disappears, 
and  it  dissolves  ,•  that  is,  it  combines  with  the  chlorine, 
forming  a  soluble  compound.  When  the  effervescence 
has  ceased,  heat  the  phial  by  placing  it  in  hot  water, 
and  afterwards  pour  its  contents  on  a  filter  of  white 
blotting-paper.  Put  the  liquid  which  passes  through 
(the  filtrate)  in  a  cool  place ;  a  salt  is  deposited  from  it 
in  greenish  crystals,  called  proto chloride  of  iron  (Fe  Cl), 
xhat  is,  iron  united  with  chlorine. 

Many  other  metals  may  also  be  dissolved,  like  iron, 
in  muriatic  acid,  and  converted  into  salts. 

Experiment  b.  —  Pour  some  muriatic  acid  upon  iron 
rust  that  has  been  put  into  a  test-tube ;  it  dissolves 
but  without  evolution  of  gas.  In  this  case,  the  hydro- 


CHLORINE  AND  HYDROGEN.  195 

gen  of  the  muriatic  acid  meets  with  a  body  with  which 
it  can  combine,  namely,  the  oxygen  of  the  oxide  of  iron; 
and  it  does  combine  with  it,  forming  water.  The  yel- 
lowish-brown solution,  which  it  is  difficult  to  crystallize, 
yields,  upon  evaporation,  a  brown  mass  called  sesquichlo- 
ride  of  iron  (Fe2  C13).  This  salt  contains  one  half  more 
chlorine  than  the  former.  Muriatic  acid  is  very  often 
used  for  dissolving  metallic  oxides. 

Experiment  c.  —  Dissolve  some  crystals  of  the  proto- 
chloride  of  iron,  obtained  according  to  experiment  #, 
in  a  little  water,  and  then  add  some  chlorine  water ;  the 
greenish  color  is  converted  into  a  yellow  color,  and  the 
solution  yields,  on  evaporation,  brown  sesquichloride  of 
iron.  The  chlorine  combines  with  the  protochloride  of 
iron,  and  makes  it  sesquichloride  of  iron. 

Experiment  d.  —  Dissolve  some  carbonate  of  soda  in 
water ;  the  solution  turns  red  test-paper  blue  ;  it  has  a 
basic  reaction.  Drop  carefully  into  the  solution  some 
muriatic  acid,  until  neither  the  red  nor  the  blue  paper  is 
affected  by  it.  Thus  muriatic  acid,  just  like  an  oxygen 
acid,  has  the  power  of  neutralizing  bases.  If  you  put 
the  liquid  in  a  warm  place,  a  salt  will  be  deposited  in 
small  cubes ;  you  readily  perceive,  both  by  the  shape  of 
the  crystals  and  by  the  taste,  that  it  is  common  salt. 
Here  also  the  oxygen  of  the  base  has  combined  with 
the  hydrogen  of  the  muriatic  acid,  forming  water,  but 
the  chlorine  with  the  sodium,  forming  common  salt. 
The  carbonic  acid  of  the  carbonate  of  soda  escapes  with 
effervescence. 

Experiment  e.  —  If  you  drop  into  a  test-tube  some 
muriatic  acid,  and  then  a  few  drops  of  a  solution  of  ni  • 
trate  of  silver  (lunar  caustic),  a  white  cloudiness  is 
formed,  which  does  not  happen  in  pure  water.  This 
cloudiness  proceeds  from  the  chloride  of  silver,  which  is 


196 


ACIDS. 


insoluble  in  water.  Nitrate  of  silver  is  the  most  accu 
rate  test  for  muriatic  acid  and  its  salts. 

If  muriatic  acid  is  diluted  with  from  800  to  900  parts 
of  water,  and  is  poured  upon  land,  it  exhibits  a  fertiliz- 
ing power,  like  that  of  sulphuric  acid  (§  173). 

187.  Haloid  Salts.  —  Like  chlorine,  the  other  salt  pro- 
ducers, or  halogens,  also  combine  with  metals  forming 
s-ilts;  these  salts  are  called  haloid  salts.  As  has  been 
shown,  they  may  be  prepared,  — 

1.)   By  uniting  a  halogen  with  a  metal  (§  156). 

2.)   By  uniting  a  halogen  with  a  metallic  oxide  (§  152). 

3.)  By  the  solution  of  a  metal  in  a  hydrogen  acid 
(§  18i5). 

4.)  By  the  solution  of  a  metallic  oxide  in  a  hydrogen 
acid  (§  186). 

If  the  two  last-mentioned  instances  be  attentively 
considered,  it  may,  perhaps,  appear  surprising  why  it 
was  not  assumed  that  muriatic  acid  combined  with  the 
base  without  further  decomposition,  just  as  it  was  as- 
sumed with  regard  to  sulphuric  acid,  and  the  other  oxy- 
gen acids.  This  cannot  generally  happen,  because 
many  of  the  haloid  salts,  when  they  are  quite  dry,  con- 
tain neither  oxygen  nor  hydrogen.  Completely  dried 
common  salt,  for  example,  contains  no  hydrochloric  acid, 
but  chlorine,  —  no  oxide  of  sodium,  but  sodium,  —  as 
has  been  ascertained  by  the  most  accurate  experiments. 
But  if  the  haloid  salts  contain  water,  or  are  dissolved  in 
water,  then  they  may  certainly  be  regarded  as  consist- 
ing of  a  base  and  a  hydrogen  acid,  for  it  amounts  to  the 
same  thing,  whether  the  hydrogen  exists  in  the  water  or 
in  the  hydrogen  acid,  the  oxygen  in  the  water  or  in  the 
metallic  oxide.  A  solution  of  salt  may  accordingly  be 
regarded  as  chloride  of  sodium  and  water,  or  as  muriate 
of  soda.  (Na  Cl  +  H  O  is  the  same  as  Na  O,  H  Cl.) 


AQUA    REGIA.  197 

Formerly  the  combinations  of  chlorine  with  the  met 
als  were  universally  called  muriates.  The  names,  muri- 
ate of  lime,  muriate  of  baryta,  muriate  of  oxide  of  iron, 
&c.,  have  therefore  the  same  signification  as  chloride  of 
calcium,  chloridg.of  barium,  chloride  of  iron,  &c.  When 
chlorine  combines  with  a  metal  in  several  proportions, 
the  combination  with  less  chlorine  is  called  protochlo- 
ride,  that  with  more  chlorine,  sesquichloride,  and  that 
with  still  more  chlorine,  perchloride  (§  154).  If  water 
is  contained  in  them,  or  if  they  are  dissolved  in  it,  the 
protochlorides  may  be  regarded  also  as  protomuriatcs^ 
and  the  perchlorides  as  permuriates  ;  for  example,  — 

Protochloride  of  iron  and  water  is  the  same  as  proto- 
muriate  of  oxide  of  iron. 

{Fe  Cl  +  H  O  =  Fe  O,  H  Cl.) 

Sesquichloride  of  iron  and  water,  the  same  as   the 
muriate  of  the  sesquioxide  of  iron. 


AQUA  REGIA,  OR  NITRO-MURIATIC  ACID  (2HC1  +  N05). 

188.  Experiment.  —  Put  into  a  flask  one  drachm  of 
nitric  acid,  and  into  another  two  drachms  of  pure 
muriatic  acid,  and  add  to  each  some  genuine  gold-leaf  ; 
it  will  not  be  dissolved.  But  if  both  liquids  are  mixed 
together,  the  gold  very  soon  disappears,  because  it  is  dis- 
solved. Gold  is  deemed  the  king  of  metals,  hence  the 
name  aqua  regia.  On  evaporating  this  solution,  a  yel- 
low salt  remains  behind,  which  consists  of  gold  and 
chlorine.  As  the  muriatic  acid  did  not  voluntarily  give 
up  its  chlorine  to  the  gold,  it  is  highly  probable  that  it 
was  compelled  to  do  so  by  the  nitric  acid.  This  process 
nriay  be  easily  explained,  if  we  refer  to  the  preparation  of 
thlorine  from  muriatic  acid  and  hyperoxide  of  manganese 
17* 


198  ACIDS. 

The  nitric  acid  acts  upon  the  muriatic  acid  just  like  the 
manganese ;  it  contains,  like  the  latter,  much  oxygen, 
and  parts  with  it  very  readily.  This  happens  also  in 
the  present  case,  and  the  liberated^  oxygen  abstracts 
from  the  muriatic  acid  its  hydrogen,  to  form  water. 
Consequently  the  chlorine  is  set  free,  which,  being  a 
simple  and  strong  chemical  body,  immediately  unites 

with  the  gold,  which  is 
likewise  a  simple  body 
The  nitric  acid  loses  there- 
by two  atoms  of  its  oxy- 
gen, and  is  converted  into 
nitrous    acid,   which   es- 
capes in  yellowish  fumes. 
Aqua  regia  is  employed  for  dissolving  gold  and  plati- 
num, neither  of  which  metals  is  attacked  by  other  acids. 

BROMINE,  IODINE,  AND  FLUORINE,  -f  HYDROGEN. 

189.  Hydrobromic  and  Hydriodic   Acids.  —  Both  of 
these  acids  closely  resemble  muriatic  acids.    Their  com- 
binations with  metals  are  called  protobromides,  perbro- 
mides,  protoiodides,  and  periodides,  &c.,  of  the  metals. 
They  occur  in  nature  accompanying  common  salt,  con- 
sequently in  sea-water  and  marine  plants,  in  salt  springs, 
&c.,  but  only  in  minute  quantities. 

190.  Hydrofluoric   Acid.  —  Experiment.  —  Rub   to   a 

powder  a  piece  of  fluor-spar,  of  the 
size  of  a  hazle-nut,  and  put  it  into 
a  small  bowl,  which  has  been  pre- 
viously rubbed  with  oiled  paper; 
then  pour  sulphuric  acid  upon  it 
till  a  thin  paste  is  formed.  Cover 
the  bowl  with  a  piece  of  window  - 


CYANOGEN  AND  HYDROGEN. 

which  has  received  a  coating  of  wax,  and  from 
some  parts  of  which  the  wax  has  been  removed  by 
scratching  with  a  needle,  or  other  pointed  instrument. 
After  the  lapse  of  some  hours,  remove  the  wax  by  melt- 
ing it,  and  then  robbing  it  off  with  oil  of  turpentine ;  those 
parts  of  the  glass  left  bare  will  be  found  to  be  corroded. 

Fluor-spar  consists  of  fluorine  and  calcium,  and  is  de- 
composed by  sulphuric  acid,  in  the  same  manner  as 
common  salt  was;  hydrofluoric  acid  is  formed  and 
escapes  in  vapor.  This  acid  has  the  property  of  dis- 
solving silica ;  therefore  it  withdraws  the  latter  from  the 
glass,  where  it  is  not  protected  by  the  wax,  and  the 
glass  consequently  becomes  rough  and  opaque.  In  this 
manner  drawings  are  often  etched  on  glass.  By  con- 
ducting the  fumes  into  water,  liquid  hydrofluoric  acid  is 
obtained,  which  may  likewise  be  employed  for  etching 
on  glass.  Lead  or  platinum  vessels  must  be  used  in  the 
preparation  of  it,  on  account  of  its  property  of  corroding 
glass  and  porcelain. 

We  also  find  fluoride  of  calcium,  in  small  quantities, 
in  the  bones  and  teeth  of  the  Mammalia, 

CYANOGEN  AND  HYDROGEN,  HYDROCYANIC  ACID  (H  Cy> 

191.  The  great  similarity  which  Cyanogen,  composed 
of  carbon  and  nitrogen,  has  to  the  halogens,  is  also 
manifested  by  its  combining  with  hydrogen,  forming  an 
acid.  This  combination  is  the  notorious  prussic  or 
hydrocyanic  acid,  a  few  drops  of  which  are  sufficient 
to  kill  instantaneously  a  small  animal.  As  muriatic 
acid  is  obtained  from  chlorides  by  sulphuric  acid,  so 
prussic  acid  is  also  obtained  from  the  cyanides  by 
means  of  sulphuric  acid,  and  it  is  also  gaseous,  like 
muriatic  acid.  To  obtain  it  in  a  liquid  form,  the  gas  is 


200  ACIDS. 

conducted  into  water,  or  alcohol,  by  which  it  is  ab- 
sorbed. It  is  colorless,  like  water,  and  it  is  easily  recog- 
nized by  its  peculiarly  oppressive  odor,  which  is  very 
similar  to  that  of  bitter  almonds.  Such  a  dangerous  ar- 
ticle should  only  be  prepared  by  experienced  workmen. 
Prussic  acid  is  found  also  in  small  quantities  in  some 
seeds,  particularly  in  bitter  almonds,  and  in  the  kernels 
of  stone  fruits,  as  plums,  apricots,  &c. 

Prussic  acid  combines  with  bases,  forming  water  and 
metallic  cyanides  (protocyanides  and  percyanides).  The 
most  familiar  of  these  are  the  yellow  ferrocyanide  of 
potassium  (prussiate  of  potassa),  and  the  blue  ferrocy- 
anide of  iron  (prussian  blue). 

EETKOSPECT  OF  THE  HYDROGEN  ACIDS. 

1.  The  haloids  or  halogens  —  chlorine,  bromine,  io- 
dine, fluorine,  and   cyanogen  —  form  acids,    not   only 
with  oxygen,  but  also  with  hydrogen. 

2.  The  halogens  have  a  greater  preference  for  hydro- 
gen than  for  oxygen ;  hence,  when  left  to  their  own  free 
will,  they  always  combine  with  the  former. 

3.  Hydrogen   unites  with  the  halogens  only  in  one 
proportion  ;  consequently,  each  of  them  forms  only  one 
single  hydrogen  acid. 

4.  All  the  hydrogen  acids  have  the  same  constitution ; 
they  always  consist  of  equal  atoms  of  a  halogen  and 
hydrogen. 

5  The  hydrogen  acids  combine  with  metals,  forming 
chlorides,  bromides,  &c.,  whilst  their  hydrogen  escapes. 

6.  The  combinations  of  the  halogens  with  the  metals 
possess  exactly  the  properties  of  salts  ;  for  this  reason 
they  are  called  haloid  salts. 

7.  The  hydrogen  acids  combine  with  the  bases,  form- 
ing haloid  salts  and  water. 


RETROSPECT.  201 

8.  If  water  is  present  in  the  haloid  salts,  they  may  be 
regarded  as  combinations   of  the  hydrogen   acids  with 
bases,  or  as  hydrogen  acid  salts,  just  as  the  oxygen  salts 
are  regarded   as   combinations   of  oxygen  acids  with 
bases. 

9.  Many  metals  may  combine  with  the  halogens  in  sev- 
eral, generally  in  two,  proportions.     When  the  halogen 
is  in  excess,  they  are  called  perchlorides,  perbromides, 
&c. ;  but  when  deficient,  they  are  called  protochlorides, 
protobromides,  &c.     The  former   correspond  with  the 
peroxide  salts,  the  latter  with  the  protoxide  salts. 

RETROSPECT  OF  THE  COMBINATIONS  OF  THE  METAL- 
LOIDS  WITH  OXYGEN  AND  HYDROGEN. 

192.  The  combinations  which  hydrogen  forms  with 
the  halogens  have  been  here  grouped  together,  because 
they  have  the  greatest  similarity  to  each  other.  These 
combinations  possess  the  distinctive  character  of  strong 
acids.  The  other  metalloids  can  also  combine  with 
hydrogen,  but  they  do  not  form  acids  with  it,  sulphur 
alone  being  an  exception,  the  combination  of  which  with 
hydrogen  certainly  comports  itself  like  an  acid,  though 
only  as  a  very  feeble  one  (§  132).  The  contrary  oc- 
curs with  nitrogen ;  this  forms  with  hydrogen  a  base, 
ammonia.  The  combinations  of  the  other  metalloids 
with  hydrogen,  some  of  which  have  already  been  treat- 
ed of  under  the  separate  metalloids,  exhibit  neither  basic 
nor  acid  properties ;  they  are,  on  this  account,  called 
neutral  or  indifferent  bodies.  Oxygen  and  hydrogen 
constitute  the  indifferent  body,  water;  carbon  and  hy- 
drogen, the  indifferent  illuminating  and  marsh  gas 
phosphorus  and  hydrogen  form  phosphuretted  hydro 
gen,  also  an  indifferent  body. 


202 


ACIDS. 


The  combinations  which  oxygen  forms  with  the  non- 
metallic  elements,  or  metalloids,  are,  indeed,  mostly  acids, 
but  we  find  among  them  some  which  possess  an  indiffer- 
ent character;  namely,  nitrous  and  nitric  oxides  (NO 
and  N  Oa),  the  oxide  of  phosphorus,  and  carbonic  oxide 
gas  (C  O).  As  is  obvious,  the  combinations  with  the  least 
quantity  of  oxygen  are  those  in  which  the  acid  properties 
are  wTanting ;  these  acid  properties  are  developed  on  the 
increase  of  the  oxygen,  and  most  strongly  in  those  com- 
binations which  contain  the  greatest  quantity  of  oxygen. 

Since  the ,  combinations  which  the  metalloids  form, 
on  the  one  side  with  oxygen,  and  on  the  other  with  hy- 
drogen, are  among  the  most  important  and  most  inter- 
esting chemical  bodies,  the  annexed  scheme  will  pre- 
sent nearly  a  correct  idea  of  the  strength  of  the  affini- 


Affinity  for  Oxygen. 
Fig.  103. 


Metalloids. 

Silicon. 

Boron. 

Carbon. 

Phosphorus. 

Sulphur. 

Selenium. 

Nitrogen. 

Cyanogen. 

Iodine. 

Bromine. 

Chlorine. 

Fluorine. 


Affinity  for  Hydrogen. 


TARTARIC    ACID.  203 

lies  which  each  of  the  metalloids  possesses  for  these  two 
elements.  The  size  of  the  circles  represents  the  affinity 
for  oxygen,  that  of  the  squares  the  affinity  for  hydrogen. 
From  this  it  is  apparent  that  the  partiality  of  the  met- 
alloids for  hydrogen  increases  in  proportion  as  it  dimin- 
ishes for  oxygen,  and  the  reverse. 

THIRD    GROUP:     ORGANIC   ACIDS. 

193.  The  oxygen  and  hydrogen  acids  are  commonly 
called  inorganic  or  mineral  acids,  because  they  are  prin- 
cipally found  in  the  mineral  kingdom,  or  prepared  artifi- 
cially from  minerals  and  earths.     But  there  are,  besides, 
many  other  acids,  found  either  already  existing  in  ani- 
mals and  plants  (formic  acid,  citric  acid),  or  which  may 
be  artificially  produced  from  organic  substances  (lactic 
acid,  acetic  acid).     Such   acids  are  called   organic,  or 
vegetable  and  animal  acids.      They  have  the  greatest 
similarity  to  the  inorganic  acids  in  their  properties  and 
combinations,  but  not  in  their  constitution.      Three  of 
them  only  will  be  treated  of  at  present  a*s  examples 
of  this  class  of  acids,  one  a  volatile,  and  the  other  two 
non-volatile  acids ;  the  others  will  be  considered  in  the 
second  and  third  parts  of  this  work. 

TARTARIC  ACID  (H  0,  f) 

194.  Tartaric  acid  has  very  much  the  appearance  of 
a  salt;  it  crystallizes  in  colorless  oblique  prisms,  which 
are  permanent  in  the  air  and  have  a  very  acid  taste. 

Experiment.  —  Place  a  small  crystal  of  tartaric  acid 
upon  a  piece  of  platinum  foil,  and  heat  it  over  the  flame 
of  a  spirit-lamp ;  it  will  first  melt,  then  become  brown, 
and  finally  black,  and  emit  at  the  same  time  a  peculiar 


204 


ACIDS. 


empyreumatic  odor.  If,  during  the 
Fig-  104>  process  of  charring,  you  hold  over 

the  acid  a  dry,  cold  glass  vessel,  it 
will  become  lined  with  globules 
of  water  ;  consequently  the  acid 
contains  oxygen  and  hydrogen. 
The  dark  residue  resembles  coal, 
but  it  is  more  certainly  deter- 
mined as  such  by  its  burning  completely  at  a  higher 
heat.  Accordingly,  tartaric  acid  has,  when  heated, 
the  greatest  similarity  to  burning  wood.  In  fact,  it 
consists  of  the  same  elements,  namely,  carbon,  hydrogen, 
and  oxygen,  but  in  different  proportions.  All  vegetable 
acids  consist  of  C,  H,  and  O,  and  are  charred  and  con- 
sumed on  being-  heated.  By  these  two  characteristics 
the  organic  acids  are  essentially  distinguished  from  the 
inorganic,  wThich  consist  only  of  two  elements,  and 
which  are  neither  charred  nor  consumed  in  the  fire. 

Experiment.  —  Pour  a  little  warm  water  over  some  tar- 
taric acid ;  it  will  dissolve  therein,  for  it  is  readily  soluble 
in  water.  If  you  dilute  the  solution  with  more  water, 
and  put  it  aside  in  a  moderately  warm  place,  slimy  flakes 
will  be  deposited,  and  the  acid  taste  will  gradually  be 
lost, — it  putrefies.  In  a  similar  manner,  ah1  organic  acids, 
when  they  are  diluted  with  water,  decompose  after  a  time. 
Experiment.  —  Mix  gradually  a  solution  of  tartaric 
acid  with  ammonia ;  there  will  be  a  period  when  the 
acid  properties  of  the  tartaric  acid  and  the  basic  ones 
of  the  ammonia  will  have  disappeared  Accordingly, 
tartaric  acid,  just  like  other  acids,  can  neutralize  bases, 
and  form  with  them  salts.  The  tartrate  of  ammonia 
obtained  is  easily  soluble. 

Experiment.  —  Neutralize  a  solution  of  carbonate  of 
ootassa  with  a  solution  of  tartaric  acid ;  the  carbonic 


TARTARIC    ACID. 


205 


acid  escapes ;  the  liquid,  however,  remains  clear,  because 
the  neutral  tartrate  of  potassa  (K  O,  T)  formed  is  an 
easily  soluble  salt.  But  by  adding  yet  more  tartaric 
acid,  the  liquid  becomes  turbid,  and  deposits  a  quantity 
of  small,  transparent  crystals,  which  are  difficultly  solu- 
ble in  water,  have  an  acid  taste,  and  contain  twice  as 
much  acid  as  the  neutral  salt,  besides,  also,  some  wa- 
ter of  crystallization.  These  crystals  are  called  acid 
tartrate  of  potassa,  or  bitartrate  of  potassa  (K  O,  2  T 
{-HO);  commonly,  tartar,  or  when  they  are  pulverized, 
cream  of  tartar.  The  salts  of  potassa  may  accordingly 
be  used  as  a  test  for  tartaric  acid. 

Tartaric  acid  is  generally  prepared  from  tartar  or 
argol,  which  is  obtained  in  large  quantities  from  the 
wine  countries,  where  it  is  deposited  from  wines  in  their 
fermenting  casks,  as  a  white  or  reddish  crust  The  po- 
tassa might  be  very  easily  removed  from  this  salt  by 
means  of  sulphuric  acid ;  but  then  two  soluble  sub- 
stances would  be  obtained,  which  could  not  well  be 
separated  from  each  other.  For  this  reason,  the  potassa 
is  first  replaced  by  another  base,  namely,  by  lime,  which 
forms  with  sulphuric  acid  an  insoluble,  or  at  least  very 
difficultly  soluble  compound.  By  boiling  tartar  with 
water,  and  adding  chalk  to  it,  then  tartrate  of  lime  is 
obtained,  as  a  white  insoluble  powder ;  if  this,  after  being 
sufficiently  washed,  is  put  by  for  some  time  with  water 
and  sulphuric  acid  in  a  warm  place  (digested),  the  ~at- 
ter  unites  with  the  lime,  and  forms  gypsum,  whilst  the 
tartaric  acid,  being  set  free,  dissolves  in  the  water,  and 
crystallizes  from  the  solution  after  evaporation. 

The  chemist  is  often  obliged  to  resort  to  such  circui- 
tous means  in  order  to  separate  two  bodies  from  each 
other,  both  of  which  are  equally  soluble  in  water  or  in 
some  other  liquid. 

18 


206  ACIDS. 

+ 

Experiment.— It  you  heat  the  crystalline  powder  of 
tartar,  obtained  in  the  former  experiment,  on  platinum 
foil,  it  will,  like  the  tartaric  acid,  become  black,  and  is 
consumed,  emitting  an  empyreumatic  odor ;  but  there 
will,  however,  finally  remain  a  white  powder,  which 
has  an  alkaline  taste,  a  basic  reaction,  and  which,  oa 
the  addition  of  an  acid,  will  effervesce  like  carbonate  of 
potassa.  The  acid  burns  up,  but  not  the  alkali ;  on  the 
combustion  of  the  acid,  carbonic  acid  is  formed,  which 
combines  with  the  potassa ;  consequently,  carbonate  of 
potassa  is  formed.  All  salts  of  the  alkalies,  or  alkaline 
earths,  with  an  organic  acid,  are  in  the  same  way  de- 
composed by  heat,  and  converted  into  carbonates. 

195.  We  can  decompose  sulphuric  acid  into  sulphur 
and  oxygen;  and  from  sulphur  and  oxygen  we  can 
again  reproduce  sulphuric  acid.  Not  so,  however,  with 
tartaric  acid ;  we  may  succeed  in  demolishing  it,  but 
it  is  beyond  our  power  to  reproduce  it  again.  We  can- 
not artificially  produce  the  organic  acids  from  their  ele- 
ments. We  are  still  ignorant  how  they  are  formed  in 
plants  and  animals.  All  that  is  known  on  this  point 
concerning  the  vegetable  acids  is,  that  they  are  formed 
from  carbonic  acid  and  water,  the  two  chief  sources  of 
the  nourishment  of  vegetables.  But  by  what  power, 
and  in  what  manner,  these  two  bodies  are  forced  to 
combine  in  the  grape-vine  to  form  tartaric  acid,  in  the 
fruit  of  the  lemon-tree  to  form  citric  acid,  in  apples  to 
form  malic  acid,  &c.,  we  are  entirely  ignorant.  We 
here  stand,  as  it  were,  on  the  boundary  line  of  our 
knowledge ;  whether  it  will  be  permitted  to  us  at  some 
future  period  to  advance  beyond  this  limit,  further  inves- 
tigations must  show.  In  the  mean  time  we  must  as- 
sume that  the  unknown  power  which  causes  the  shoots, 
leaves,  and  blossoms  to  put  forth  from  the  seeds,  —  we 


OXALIC    ACID. 


207 


call  it  vital  power,  —  is  also  able  to  produce  chemical 
combinations  and  decompositions  more  powerful  and 
manifold  than  it  is  possible  for  the  chemist  to  accom- 
plish in  his  retorts  and  crucibles.  In  this  sense  we  re- 
gard the  organic  acids,  as  in  general  all  organic  sub- 
stances, as  the  chemical  productions  of  the  vital  activity 
of  plants  and  animals. 

The  organic  acids  are  briefly  designated  by  a  horizon- 
tal line  placed  above  their  initials.  The  Latin  name  for 
tartar  is  tartarus  ;  the  symbol  for  tartaric  acid  is  T. 


OXALIC  ACID  (H  0,  O,  or  H  O, 

196.  Experiment.  —  Heat  with  free  access  of  air,  in  a 
porcelain  dish,  one  fourth  of  an  ounce  of  sug- 

Fig.  105.  .  ' 

ar,  mixed  with  one  and  a  hall  ounces  ol  con- 


centrated nitric  acid,  and  one  ounce  of  water. 
In  a  short  time  a  strong  evolution  of  yellow- 
ish-red fumes  (N  O3)  will  commence.  Con- 
tinue boiling  until  these  vapors  cease,  and 
then  put  the  liquid  in  a  cool  place ;  colorless 
crystals  (right  rhombic  prisms)  will  be  sepa- 
rated, which  must  be  purified  by  recrystalli- 
zation.  They  have  an  intensely  strong  acid 
reaction,  and  are  poisonous ;  they  are  called 
oxalic  acid.  This  acid,  like  most  acids,  contains  water 
chemically  combined,  without  which  it  cannot  exist. 

Experiment.  —  Pour  into  a  test-tube  twenty  grains  of 
oxalic  acid,  and  one  drachm  of  fuming  oil  of  vitriol,  and 
carefully  heat  the  mixture ;  a  gas  will  be  evolved.  Let 
this  pass  through  lime-water  contained  in  another  test- 
tube.  One  half  of  the  escaping  gas  is  absorbed  by  the 
lime-water,  which  thereby  becomes  turbid;  this  is  car- 
bonic acid  (C  O2).  The  other  half  escapes  through  the 


208  ACIDS. 

open  tube,  and  burns,  when  kindled,  with  a  bluish 
flame;  this  is  carbonic  oxide  gas  (CO).  When  the 
evolution  of  the  gas  ceases,  there  will  be  found  in  the 
first  test-tube  common  sulphuric  acid ;  consequently, 
the  fuming  oil  of  vitriol  has  received  water,  namely,  the 
chemically  combined  water  contained  in  the  oxalic  acid. 
The  oxalic  acid,  when  it  loses  its  water,  is  resolved  into 
the  two  gases  just  mentioned ;  it  may,  accordingly,  be 
regarded  as  a  combination  of 

1  atom  C  O2, 
and  1  atom  C  O, 
or     C2  O3. 

On  comparing  this  constitution  with  that  of  sugar, 
it  will  be  seen  that  the  sugar  contains  still  more  carbon 
than  the  oxalic  acid,  besides  some  hydrogen;  conse- 
quently a  portion  of  its  carbon,  and  all  its  hydro- 
gen, must  have  been  withdrawn.  This  was  done  by 
the  oxygen  of  the  nitric  acid,  which  oxygen,  uniting 
with  the  carbon,  formed  carbonic  acid,  and  with  the 
hydrogen,  formed  water.  This  process  may  be  regard- 
ed as  a  combustion  (oxidation)  in  the  moist  way.  Sug- 
ar has  exactly  the  same  constituents  as  wood.  If 
a  wood-shaving  be  ignited,  at  first  the  hydrogen  princi- 
pally burns,  because  it  is  very  readily  combustible ;  at 
last  principally  the  carbon,  because  this  burns  with 
more  difficulty  (§  120).  The  same  succession  of  phe- 
nomena also  takes  place  on  the  boiling  of  sugar  with 
nitric  acid ;  the  hydrogen  is  at  first  principally  oxidized, 
and  afterwards  the  carbon ;  but  the  latter  only  partially, 
on  account  of  the  insufficient  supply  of  nitric  acid,  just 
as  wood  is  only  partially  consumed  when  there  is  a  de- 
ficiency in  the  supply  of  the  air.  The  partly  consumed 
wood  (charcoal)  burns  completely  if  we  heat  it  still 
'onger  in  the  air ;  it  is  converted  into  carbonic  acid  by 


OXALIC    ACID.  209 

the  oxygen  of  the  air.  Partly  burnt  sugar  (oxalic  acid) 
consumes  completely  when  we  boil  it  with  still  more 
nitric  acid  ;  it  is  converted  into  carbonic  acid  by  the 
oxygen  of  the  nitric  acid. 

11)7.  Experiments  with   Oxalic  Acid. 

Experimenfoa. —  Place  some  crystals  of  oxalic  acid 
upon  a  piece  of  platinum  foil,  and  hold  them  in  the 
flame  of  a  spirit-lamp.  They  melt,  inflame,  and  burn 
without  becoming'  black  or  leaving  any  residue.  The 
product  of  the  combustion  is  carbonic  acid ;  C2  O3  and 
O  (from  the  air)  are  converted  into  2  C  O2. 

Experiment  b.  —  Neutralize  a  hot  concentrated  solu- 
tion of  oxalic  acid  with  a  hot  concentrated  solution  of 
carbonate  of  potassa;  neutral  oxalate  of  potas"sa  (KO, 
C2  O3),  an  easily  soluble  salt,  is  formed.  If  you  now  add 
as  mueh  more  oxalic  acid,  hard  crystals  will  be  depos- 
ited on  cooling,  which  have  an  acid  reaction  ;  they  are 
called  acid  oxalate,  or  binoxalate  of  potassa.  One  atom 
of  potassa  can  thus  combine  with  two  atoms  of  acid. 
As  has  been  previously  stated,  salts  with  two  atoms  of 
acid  are  called  acid  salts.  The  binoxalate  of  potassa  is 
likewise  formed  in  the  substance  of  many  plants  during 
their  growth,  and  it  is  found  abundantly  in  the  leaves 
of  the  wood-sorrel  (Oxalis),  from  which  it  may  be  ob- 
tained. The  acid  salt  is  far  less  soluble  than  the  neutral. 

Experiment  c.  —  Heat  some  binoxalate  of  potassa 
upon  platinum  foil ;  like  the  tartar,  it  will  be  converted 
into  carbonate  of  potassa,  but  without  being  charred  or 
blackened.  The  oxalic  acid  is  thereby  converted,  as 
above,  into  carbonic  acid  and  carbonic  oxide,  and  a 
portion  of  the  former  combines  with  the  potassa. 

Experiment  d.  —  Agitate  a  little  gypsum  with  water 
and  let  the  liquid  settle ;  the  decanted  water  contains  a 
small  quantity  (^)  of  gypsum  in  solution.  If  a  solution 
18* 


210 


ACIDS. 


Fluid. 


Solid. 


Soluble. 


of  oxalic  acid  is  poured  upon  this  solution  of  gypsum, 
you  will  soon  obtain  a  precipitate  of  oxalate  of  lime  ; 

consequently  oxalic  acid 
has  a  greater  affinity  for 
lime  than  sulphuric  acid 
has,  since  it  is  able  to 
displace  the  latter  acid. 
The  decomposition  takes 

place  more  rapidly  and  perfectly  when  the  oxalic  acid 
has  been  previously  neutralized  by'  ammonia  (N  H3), 

because  another  body 
is  thus  presented  to 
the  sulphuric  acid,  for 
which  the  latter  has 
a  greater  affinity  than 
for  the  watery  it  be- 
comes thereby  more  ready,  as  it  were,  to  release  the 
lime.  Oxalic  acid  is  the  best  test  for  lime  and  lime  salts. 
Experiment  e.  —  Add  some  spoonfuls  of  water  to  a 
piece  of  green  vitriol  of  the  size  of  a  pea,  and  moisten 
with  the  solution  a  piece  of  white  blotting-paper;  when 
this  has  imbibed  the  liquid,  spread  over  it  some  ammo- 
nia. The  ammonia  withdraws  the  sulphuric  acid  from 
the  green  vitriol,  and  protoxide  of  iron  must  conse- 
quently be  separated  in  and  upon  the  paper,  to  which 
it  imparts  a  greenish  tinge.  On  drying,  the  protoxide 
of  iron  becomes  converted  into  sesquioxide  of  iron, 
and  the  green  color  is  at  the  same  time  changed  to 
yellow.  In  a  similar  manner,  cotton,  and  other  fab- 
rics, are  often  dyed  brown  or  yellow.  Mix  some  oxalic 
acid  with  water  into  a  thin  paste,  and  dot  the  yellow 
paper  with  it  in  several  places ;  the  color  will  soon  dis- 
appear from  those  spots,  and  you  obtain  a  white  pattern 
on  a  yellow  ground.  Oxalic  acid  easily  dissolves  seb- 


ACETIC    ACID.  21.1 

quioxide  of  iron,  and  both  are  removed  by  washing. 
TInon  this  is  founded  the  important  use  of  this  acid  in 
calico  printing,  as  likewise  its  application  for  the  re- 
moval of  ink-spots  from  linen  or  paper.  One  of  the 
principal  constituents  of  ink  is  oxide  of  iron,  which  be- 
ing dissolved  l^y  oxalic  acid,  the  black  color  of  the  ink 
disappears  also.  This  explains  why  oxalic  acid,  or  an 
oxalate  containing  a  free  acid,  causes  the  white  spots 
on  fabrics  dyed  yellow  by  peroxide  of  iron,  and  also 
why  it  removes  ink-spots  from  garments,  paper,  &c. 


ACETIC  ACID  (HO, A). 

198.  Vinegar  is  likewise  a  vegetable  acid.  It  is  often 
formed  spontaneously,  producing  mischievous  conse- 
quences. It  is  formed  when  sweet  or  spirituous  liquors, 
thin  syrups,  the  juice  of  fruit,  wine,  beer,  &c.,  remain 
exposed  to  the  air.  The  sugar  is  converted  by  degrees 
into  alcohol,  which  becomes  vinegar  when  access  to  the 
oxygen  of  the  air  is  not  prevented.  But  the  method  by 
which  this  takes  place  will  not  be  considered  until  sug- 
ar and  alcohol  are  treated  of.  We  shall  now  merely 
describe  the  method  of  preparing  acetic  acid  from  crude 
vinegar. 

Our  common  vinegar  contains  in  every  pound  only 
from  half  an  ounce  to  two  ounces  of  acetic  acid ;  the 
rest  is  water.  If  you  boil  vinegar,  the  acid  smell  of  the 
fumes  indicates  that  the  acid  contained  in  it  is  volatile ; 
therefore  it  cannot,  like  other  acids,  be  made  stronger  by 
evaporation ;  but  this  may  be  done  in  the  following 
manner. 

Experiment.  —  Add  to  one  pound  of  colorless  vinegar 
from  one  to  one  and  a  half  ounces  of  litharge  (oxide  of 
lead),  and  let  t!fe  mixture  stand  in  a  vessel  for  some 


212 


ACIDS. 


hours,  in  a  warm  place,  stirring  it  frequently.  The 
liquid  will  become  clear  on  standing,  and  then  if  you 
evaporate  it  down  to  two  and  a  half  or  three  ounces, 
and  let  it  cool,  prismatic  crystals  of  acetate  of  oxide  of 
lead  will  be  deposited.  This  salt  is  commonly  called 
sugar  of  lead  from  its  sweetish  taste.  The  acetic  acid  is 
held  so  firmly  by  the  oxide  of  lead,  that  it  can  no  longer 
escape  with  the  steam  during  evaporation,  or  at  least 
only  in  trifling  quantities.  Other  bases  may  be  substi- 
tuted for  the  oxide  of  lead. 

Experiment.  —  Place  upon  a  piece  of  charcoal  some 
sugar  of  lead,  and  heat  before  the  blow-pipe  ;  the  salt 
first  melts  in  its  water  of  crystallization,  then  it  becomes 
brown,  and  is  finally  charred ;  the  acetic  acid  is  thus 
decomposed,  like  tartaric  acid  on  the  heating  of  the  salts 
of  tartaric  acid.  After  being  completely  burnt,  globules 
of  metallic  lead  remain  upon  the  coal.  The  litharge  is 
also  decomposed ;  the  glowing  coal  abstracts  from  it  its 
oxygen,  and  forms  with  it  carbonic  oxide  gas,  which 
escapes ;  consequently  metallic  lead  must  remain  behind 
(reduction  or  deoxidation). 

Experiment.  —  Mix  cautiously  half  an  ounce  of  sul- 

Fig.  106. 


ACETIC    ACID.  213 

phuric  acid  with  half  an  ounce  of  water,  and  when  cold 
pour  the  mixture  into  a  flask  containing  one  ounce  of  pul- 
verized sugar  of  lead.  Now  connect  a  glass  tube  and 
receiver  with  the  flask,  and  distil  the  mixture  at  a  mod- 
erate heat,  on  a  sand-bath,  until  about  three  fourths  of 
an  ounce  of  the  fluid  has  passed  over.  This  presents 
an  example  of  simple  elective  affinity;  the  strong  sul- 
phuric acid  unites  with  the  oxide  of  lead,  and  forms 
with  it  a  white,  insoluble  compound,  which  remains  in 
the  flask,  while  the  acetic  acid,  rendered  volatile  by 
the  heat,  is  converted  into  steam,  which  is  condensed 
in  the  cold  receiver  into  liquid  acetic  acid. 

The  acid  thus  obtained  is  colorless,  and  has  an  ex- 
ceedingly sour  taste  and  smell.  The  strongest  acetic 
acid  (hydrated  acetic  acid)  crystallizes  on  cooling;  a 
somewhat  diluted  acetic  acid  is  called  concentrated 
vinegar. 

Experiment.  —  Add  to  strong  acetic  acid  some  drops 
of  oil  of  cinnamon,  and  cloves ;  if  the  acid  was  suffi- 
ciently strong  they  will  dissolve.  This  mixture  is  called 
aromatic  spirit  of  vinegar. 

Experiment.  —  Pour  some  acetic  acid  upon  a  piece 
of  lean  meat,  and  it  will  gradually  become  soft  and 
gelatinous.  Common  vinegar  has  also  the  same  effect, 
but  in  a  less  degree ;  it  is  indeed  well  known,  that  meat 
impregnated  with  vinegar  becomes  very  tender  and  di- 
gestible (soluble)  when  boiled  or  roasted. 

Acetic  acid  cannot  exist  without  the  presence  of  wa- 
ter ;  seven  ounces  of  the  strongest  acid  contain  one 
ounce  of  water  chemically  combined.  The  Latin  w  ord 
for  vinegar  is  acetum;  the  symbol  for  acetic  acid  is,  ac- 
cordingly, H  O,  A. 

To  detect  the  salts  of  acetic  acid,  heat  them  in  a  t<  st- 
tube  with  concentrated  sulphuric  acid ;  when  fumes 
Having  a  very  acid  smell  will  be  evolved. 


214  ACIDS. 

RETROSPECT  OF  THE  VEGETABLE  ACIDS. 

1 .  Almost  all  vegetable  acids  consist  of  carbon,  hy 
dwgen,  and  oxygen  (oxalic  acid  being  an  exception.) 

2.  They  are  generated  during  the  growth  of  plants, 
in  which  they  are  found  either  free  or  combined  with 
bases. 

3.  We  cannot  artificially  prepare  them   from  their 
elements,  like  the  inorganic  acids. 

4.  Some  vegetable  acids  may  indeed  be  also  artifi- 
cially imitated,  but  as  a  general  rule  this  is  effected  by 
the  metamorphosis  of  other  vegetable  substances. 

5.  All  vegetable  acids  are  charred  by  heat,  and  are 
at  last  completely  consumed  (inorganic  acids  are  not). 

6.  Most  vegetable   acids   cannot  exist  without  the 
presence  of  water  (water  of  constitution) ;  this  water 
plays  therein  the  part  of  a  base. 

7.  Vegetable  acids  comport  themselves  towards  bases 
like  the  inorganic  acids  ;  they  form  with  them  salts. 

8.  The  vegetable  salts  are  likewise  decomposed  by 
heat ;  the  acid  is  charred  and  consumed,  while  the  base 
remains  behind,  usually  combined  with  carbonic  acid.  J 

RADICALS.  — CAPACITY    OF   NEUTRALIZATION. 

199.  The  word  radical  signifies  root  or  base,  and  ia 
often  employed  in  chemistry  to  denote  that  substance 
which  is  regarded  as  the  fundamental  element  or  base 
of  a  chemical  compound.  The  metalloids  unite  with 
oxygen,  and  some  of  them  also  with  hydrogen,  forming 
acids,  and  they  are  consequently  regarded  as  the  bases 
of  the  acids,  and  may  be  called  the  acid  radicals.  Sul- 
phur is  accordingly  the  radical  of  sulphuric  acid ;  car- 
bon, of  carbonic  acid ;  and  chlorine,  of  chloric  and 


RADICALS.  215 

muriatic  acids,  &c.  With  regard  to  the  vegetable 
acids,  which  are  composed  of  three  elements,  carbon, 
hydrogen,  and  oxygen,  if  the  oxygen  be  assumed  as  the 
acidifying  principle,  then  the  carbon  and  hydrogen  are 
regarded  as  the  acid  radicals ;  or  if  hydrogen  be  con- 
siderecTthis  principle,  then  carbon  and  oxygen  would 
be  the  radicafe.  In  either  case  the  radical  consists  of 
two  elements ;  and  for  this  reason  the  vegetable  acids 
are  said  to  be  adds  with  a  compound  radical,  in  contra- 
distinction to  the  mineral  acids,  which  are  regarded  as 
acids  witli  a,  simple  radical,  because  they  have  only  one 
element  for  their  base.  According  to  this  classification 
the  hydrocyanic  and  fulminic  acids  must  be  classed 
among  the  acids  with  compound  radicals,  since  the  rad- 
ical cyanogen  is  composed  of  carbon  and  nitrogen. 

This  theory  is  also  applied  to  bases  and  salts.  The 
metals  combine  with  oxygen,  forming  bases,  and  are 
accordingly  the  fundamental  elements  of  the  bases, — 
basic  radicals.  Iron,  for  example,  is  the  radical  of  the 
oxide  of  iron,  and  calcium  the  radical  of  lime.  The 
oxide  or  the  base  is  regarded  as  the  fundamental  ele- 
ment of  the  salts  ;  it  has  received  the  name  salt  radical. 
Protoxide  of  iron  is  accordingly  the  radical  of  green  vit- 
riol, lime  that  of  chalk,  &c. 

200.  It  has  already  been  demonstrated,  by  several  ex- 
periments, that  the  acids  are  neutralized  or  saturated 
by  bases,  and  also  that  every  acid  on  neutralization 
combines  with  a  definite  quantity  only  of  a  base.  It 
now  remains  to  consider  how  large  this  quantity  may 
be  for  every  acid. 

It  has  been  ascertained,  by  accurate  experiments, 
that  100  ounces  of  sulphuric  acid  require  for  neutral- 
ization exactly  118  ounces  of  potassa,  or  70  ounces  of 
lime,  or  90  ounces  ol  protoxide  of  iron,  or  278  ounces 


216 


ACIDS. 


of  litharge.  Further  researches  have  led  also  to  the 
surprising  discovery,  that  these  so  unequal  quantities  of 
the  different  bases  contain  precisely  the  same  amount 
of  oxygen,  namely,  20  ounces. 

Sulphuric  Acid  Oxygen. 

100  oz.  are  neutralized  by  118  oz.  of  potassa  ;  these  contain  20  oz. 

100  "      "          "  "      70  "    "  lime ;  "          "        20  " 

100  "      "          "  "      90  "    "  protoxide  of  iron;"          "        20  " 

100  "      "          «  "    278  "    «  oxide  of  lead ;       "          "        20  " 

It  follows  as  a  law  for  sulphuric  acid,  that  100 
ounces  of  it  require  always  for  neutralization  a  quantity 
of  some  base  in  which  are  contained  20  ounces  of  oxy- 
gen. Thus  the  number  20  has  been  called  the  capacity 
of  neutralization  of  sulphuric  acid. 

The  action  of  bases  upon  all  the  other  acids  has  been 
examined  in  the  same  manner,  and  the  capacity  of 
neutralization  of  the  latter  determined.  That  of  nitric 
acid,  for  example,  is  14f ;  that  of  carbonic  acid,  36^ ; 
that  is,  every  quantity  of  any  base  containing  exactly 
14f  ounces  of  oxygen  is  able  to  saturate  or  neutralize 
100  ounces  of  nitric  acid ;  every  quantity  of  a  base  con- 
taining 867  ounces  of  oxygen  is  able  to  saturate  or 
neutralize  100  ounces  of  carbonic  acid. 

Instead  of  comparing,  as  has  been  done  here,  the 
acids  with  the  oxygen  of  the  base,  the  oxygen  of  the 
acid  is  also  sometimes  compared  with  the  oxygen  of  the 
base. .  This  may  be  done  very  easily,  if  we  only  know 
in  the  first  place  how  much  oxygen  is  contained  in  100 
ounces  of  an  acid. 

Oxygen  Oxygen. 

100  oz.  of  sulphuric  acid  contains  60    oz.,  and  require  in  the  base  20  oz. 
100   "    "  nitric  acid  "        73|   "      "          "          "          "     Hi  " 

100   "    "   carbonic  acid        "        72$   «      "          «          "          "    36| « 

And  hence  may  be  deduced  the  following  simple  pro- 
portion for  the  combination  of  the  acids  with  the  bases, 
khat  is,  for  the  salts. 


POTASSIUM. 


217 


The  oxygen  of  the  add  bears  the  proportion  to  the 
oxygen  of  the  bases :  — 

In  all  neutral  sulphates,   as  60   to  20,  or  as  3  to  1. 
«  "        nitrates,        "  73|   «  14|,  "     "  5  «  1. 

"  «        carbonates,  «  72j   "  36|,  "     «  2  «  1. 

Water  acts  also  as  a  base  when  chemically  com- 
bined with  an  acid.  In  common  sulphuric  acid  (HO, 
S  O3),  for  example,  the  oxygen  of  the  acid  bears  a  pro- 
portion to  the  oxygen  of  the  water  as  3  to  1 ;  in  the 
strongest  nitric  acid  (H  O,  N  O5),  as  5  to  1,  &c. 


LIGHT   METALS. 

FIRST  GBOUP:     ALKALI-METALS. 

POTASSIUM  (K). 
At.  Wt.  —  489.  —  Sp.  Gr.  =  0.8. 

201.  Potash,  or  Carbonate  of  Potassa  (K  O,  C  O.). 
Experiment.  —  Fit  into  a  funnel  a  filter  of  blotting- 
paper,  and  place  upon  it  a  handful  of  wood- 
Fig,  lor.        ashes,  and  gradually  pour   hot   water  over 
them ;  the  liquid  filtered  through  has  an  al- 
kaline taste,  and  turns  red  test-paper  blue. 
If  you  evaporate  it  to  dryness  in  a  porcelain 
dish,  a  gray  mass  finally  remains  behind, 
which  becomes  white  after  being  heated  to 
redness  in  a  porcelain  crucible ;  it  is  called 
crude    potash.      In  those    countries   where 
wood   is   abundant,  —  in  America,    Russia, 
&c.,  —  it  is  prepared  in  a  similar  manner  on  a  large 
scale,  and  is  an  article  of  great  demand  in  commerce. 
19 


218 


ALKALIES. 


There  are  to  be  found  in  ashes  (§  607)  all  the  sub- 
stances which  the  plants  received  from  the  soil  during 
their  growth  ;  they  are  not  volatile,  and  therefore  remain 
behind  while  the  characteristic  parts  of  the  wood  or  plant 
are  consumed.  The  soluble  portion  of  the  ashes  is 
taken  up  by  the  water  (potash  and  other  soluble  salts) ; 
those  which  are  insoluble  (silica,  insoluble  salts,  and 
unburnt  pieces  of  coal)  remain  behind  on  the  filter. 

Experiment.  —  Pour  half  an  ounce  of  cold  water  upon 
half  an  ounce  of  commercial  potash,  stir  it  frequently, 
and  let  it  stand  for  one  night.  Separate  the  liquid  by 
nitration  from  the  sediment,  which  consists  principally 
of  silica;  evaporate  it  down  to  one  half,  and  again 
leave  it  in  repose  for  one  night,  when  most  of  the  for- 
eign salts  will  be  deposited  in  crystals.  Again  filter 
the  liquid  and  evaporate  to  dryness,  continually  stirring 
with  a  glass  rod,  and  you  will  obtain  a  white  granulated 
mass,  purified  potash. 

Potash  is  very  easily  soluble ;  therefore  it  is  the  first  ol 
the  ingredients  which  is  taken  up  by  water,  and  the 
last  which  is  separated  from  it ;  but  the  other  admix- 
tures are  much  less  so,  and  they  remain  partly  undis- 
solved,  and  partly  separate  in  crystals  from  the  liquid, 
before  the  potash  shows  even  the  slightest  tendency  to 
crystallize.  There  are  thus  two  methods  ty  which 
substances  of  different  degrees  of  solubility  may  be 
separated  from  each  other. 

202.  Experiments  with  Potash. 

Experiment  a.  —  Put  one  portion  of  potash  in  a  ves- 
sel, and  let  it  stand  in  a  dry  apartment,  and  put  an- 
other portion  in  a  cellar ;  the  former  becomes  moi&t,  the 
latter  deliquesces.  Both  attract  water  from  the  air,  but 
that  in  the  dry  atmosphere  of  the  room  less  than  that 
in  the  damp  air  of  the  cellar.  Potash  is  a  very  hygro- 
scopic salt. 


POTASSIUM. 

Experiment  b. —  Boil  for  some  time,  in  a  vessel 
containing  a  quarter  of  an  ounce  of  potash  and  two 
ounces  of  water,  a  piece  of  gray  linen,  and  some  dirty  o 
greasy  linen  or  cotton  rags;  the  liquid  will  become  ol 
a  dark  color,  while  the  rags  are  made  white  and  clean. 
Dirt,  as  it  is  commonly  called,  is  dust,  which  adheres 
to  the  skin,  garments,  &c.,  particularly  after  they  have 
become  moistened  by  perspiration,  or  have  come  in 
contact  with  greasy  or  other  adhesive  substances. 
These  last-mentioned  substances  may  be  dissolved  and 
removed  by  potash  ;  on  this  depends  the  various  appli- 
cation of  this  substance  in  cleaning  and  washing. 

Experiment  c.  —  Pour  a  teaspoonful  of  potash  into  a 
tumbler  containing  vinegar;  there  escapes  with  brisk 
effervescence  a  gas,  in  which  a  burning  taper  is  ex- 
tinguished. This  gas  is  the  well-known  carbonic  acid, 
it  is  chemically  combined  in  the  potash  with  the  basic 
oxide  of  potassium  or  potassa.  Potash  is  consequently 
a  salt,  carbonate  of  potassa  (K  O,  C  O.,) ;  but  beside 
this,  the  crude  potash  contains  also  several  other  foreign 
salts,  as  silicate,  sulphate,  muriate,  and  phosphate  of 
potassa,  and  many  others.  The  feeble  carbonic  acid  is 
not  able  to  destroy  completely  the  basic  properties  of 
the  potassa ;  therefore  the  carbonate  of  potassa  has  an 
alkaline  taste,  and  colors  red  litmus-paper  blue.  Vin- 
egar can  completely  neutralize  potassa.  If  you  add  so 
much  of  it  to  the  potassa,  that  neither  blue  nor  red 
test-paper  is  altered,  and  then  filter  and  evaporate  the 
liquid,  you  will  obtain  a  white  saline  mass,  —  acetate  oj 
potassa. 

We  might  suppose  that  the  carbonic  acid,  which  so 
willingly  assumes  a  gaseous  form,  might  easily  be  ex- 
pelled by  heating ;  but  it  is  a  striking  fact,  that  its 
friendship  for  the  potassa  stands  the  proof  even  of  the 


220 


ALKALIES. 


hottest  fire.     The  potash  does  not  lose  its  carbonic  acid 
at  the  strongest  red  heat. 

The  potash  of  commerce  possesses  very  different  de- 
grees of  goodness  and  purity.  To  test  its 
value,  or  to  compare  several  sorts  with 
each  other,  weigh  one  hundred  grains  of 
each  sort,  and  neutralize  them  with  an 
acid.  A  good  article  requires  more  acid 
than  a  bad  one;  consequently  the  value  of 
the  potash  may  be  "estimated  according  to 
50  the  quantity  of  the  acid  consumed.  An 
alkalimeter  is  a  useful  instrument  for  those 
who  have  frequently  to  determine  the  value 
of  potash.  It  consists  of  a  glass  cylinder, 
divided  into  degrees  (graduated)^  in  which 
the  quantity  of  acid  is  measured  instead  of 
being  weighed.  For  this  purpose  a  test-acid  must  be 
prepared,  of  such  a  strength  that  one  degree  of  it  will 
exactly  neutralize  one  grain  of  pure  carbonate  of  po- 
tassa.  The  number  of  degrees  of  the  acid  consumed 
will  then  indicate  at  once,  in  per  cent,  the  quantity  of 
pure  carbonate  of  potassa  in  the  sample  tested.  The 
value  of  soda  may  be  ascertained  in  a  similar  way 

Bicarbonate  of  Potassa  (KO,  2  CO2  +  HO). 

If  carbonic  acid  is  conducted  into  a  solution  of  car- 
bonate of  potassa,  the  latter  will  take  up  as  much 
again  carbonic  acid  as  it  previously  contained,  and 
crystals  will  be  deposited,  consisting  of  one  atom  of 
potassa,  two  atoms  of  carbonic  acid,  and  one  atom 
of  water.  This  combination  belongs,  accordingly, 
to  the  acid  salts.  On  heating,  the  second  atom  'oi 
carbonic  acid,  together  with  the  water,  escapes ;  and 
the  same  happens,  in  Dart,  on  boiling  a  solution  of  this 
Bait 


POTASSIUM. 


22) 


203.   Oxide  of  Potassium,  or  Potassa  (K  O). 
If  you  withdraw  the  carbonic  acid  from  the  potash, 
potassa  remains  behind. 

Experiment.  —  Place  half  an  ounce  of  quicklime  in  a 
piate,  drench  it  with  warm  water,  and  let  it  stand  until 
it  is  slaked,  that  is,  until  it  be- 
comes a  fine  dusty  powder.  Then 
put  half  an  ounce  of  potash  into 
an  iron  basin  with  six  ounces  of 
water,  and  boil  it,  and  gradually 
add  by  spoonfuls,  during  the  boil- 
ing, half  of  the  slaked  lime.  After 
the  mixture  has  boiled  for  some 

time,  put  a  teaspoonful  of  it  upon  a  paper  filter,  and 
pour  the  filtrate  into  vinegar.  If  it  effervesces,  still 
more  lime  must  be  added ;  but  if  no  effervescence  en- 
sues, pour  the  whole  into  a  bottle,  close  it  up,  and  let  it 
remain  quiet  for  some  hours,  that  the  sediment  may 
subside.  Decant  the  clear  liquor,  and  preserve  it  in  a 
well-stoppered  bottle.  It  consists  of  water  in  which 
potassa  is  dissolved,  and  is  called  solution  of  caustic  po- 
, or  lye.  The  carbonic  acid  previously  combined 

with  the  potassa  has 
soluble,  during  the  boiling  pass- 
ed to  the  lime,  as  may 
e  easily  be  seen  by  the 
effervescence  which  en- 
sues when  vinegar  or  some  other  acid  is  poured  on 
the  white  sediment  of  lime.  From  the  lime,  carbonate 
of  lime  is  formed,  but  potassa  from  the  carbonate  of 
potassa.  The  carbonate  of  lime-  is  insoluble,  and  ia 
deposited  as  a  white  powder;  the  potassa  is  soluble, 
and  it  combines  with  the  water  present. 
19* 


222 


ALKALIES. 


It  would  thus  appear  as  if  lime  were  a  stronger  base 
than  potassa,  since  it  takes  from  the  latter  the  carbonic 
acid;  but  this  is  not  correct,  for  in  all  other  cases  the 
potassa  is  stronger  than  lime.  But  a  weaker  base, 
u'hcn  it  forms  with  an  acid -an  insoluble  salt,  always  takes 
this  acid  even  from  a  much  stronger  base.  Thus  the 
lime  abstracts  the  carbonic  acid  from  the  potassa,  not 
because  it  has  a  greater  affinity  for  the  acid,  but  be- 
cause it  forms  with  it  an  insoluble  compound  (chalk). 
In  the  same  way  a  weaker  acid  is  often  able  to  over- 
come a  stronger  one. 

Experiment. —  Evaporate  a  portion  of  the  caustic 
potassa  in  an  iron  vessel  (glass  and  porcelain  are  at- 
tacked by  it)  ;  all  the  water  but  one  atom  escapes,  and 
a  white  mass  finally  remains  behind,  hydrate  of  potassa. 
This  may  be  melted  at  a  stronger  heat,  and  cast  into 
sticks  or  plates  (lapis  inf emails,  or  fused  potassa). 

Potassa  consists  of  a  metal  (potassium)  and  oxygen 
(§  166).  It  also  contains  one  sixth  of  its  weight  of 
water,  which  cannot  be  expelled  even  by  the  strongest 
heat ;  its  proper  name  is,  accordingly,  hydrate  of  potas- 
sa (K  O,  HO).  This  water,  as  though  it  were  an  acid, 
is  chemically  combined  with  the  potassa.  Water,  be- 
ing an  indifferent  body,  acts  with  strong"  bases  like  an 
acid,  and  with  strong-  acids  like  a  base  (§  200). 

204.  Experiments  with  Hydrate  of  Potassa. 

Experiment  a.  —  Expose  some  dry  potassa  to  the  air ; 
it  will  soon  become  moist ;  indeed,  it  will  deliquesce, 
and  on  longer  exposure  it  will  effervesce  upon  the  addi- 
tion of  an  acid.  Potassa  has  two  strong  affinities :  1st, 
for  water ;  2d,  for  carbonic  acid.  It  absorbs  both  from 
the  air,  and  is  then  converted  into  carbonate  of  potassa. 

Experiment  b.  —  Heat  in  one  test-tube  some  white 
and  in  another  some  brown  blotting-paper,  with  some 


POTASSIUM.  223 

potassa  lye ;  both  papers  will  be  decomposed  and  dis- 
solved, the  vegetable  fibres  of  the  white  paper  (linen  or 
cotton)  more  slowly  than  the  animal  fibres  of  the  brown 
paper  (wool).  Potassa  exerts  a  very  corrosive  action, 
especially  on  animal  substances.  The  slippery  feeling 
caused  by  rubbing  lye  between  the  ringers  is  owing  to 
a  gradual  solution  of  the  skin. 

Experiment  c.  —  Boil  in  a  test-tube  a  little  tallow  or 
fat  with  a  solution  of  caustic  potassa;  a  union  grad- 
ually takes  place  ;  soap  is  formed.  The  soap  prepared 
from  potassa  is  soft,  and  is  called  barrel-soap  or  soft- 
soap. 

Experiment  d.  —  If  some  potassa  be  melted  with  sand 

on  a  piece  of  charcoal, 
Fig-  no-  before    the    blow-pipe, 

we  obtain  a  vitreous, 
amorphous  compound 
of  silicate  of  potassa. 
Much  sand  and  a  small 
proportion  of  potassa 
yield  an  insoluble  glass, 
—  the  common  bottle 
or  window  glass;  but 
much  potassa  with  a 
small  proportion  of  sand,  a  soluble  compound,  called 
soluble  glass.  A  solution  of  the  latter  may  be  em- 
ployed as  a  fire-proof  varnish  for  wood,  canvas,  and 
other  combustible  materials. 

Experiment  e.  —  Dissolve  a  piece  of  blue  vitriol  (sul- 
phate of  copper)  in  water,  and  add  to  it  some  potassa 
lye.  Potassa  is  the  strongest  base  known ;  therefore  it 
abstracts  the  sulphuric  acid  from  the  blue  vitriol,  and 
forms  with  it  sulphate  of  potassa,  which  remains  in 
solution.  The  oxide  of  copper,  not  being  soluble  in 


224  ALKALIES. 

water  without  an  acid,  is  precipitated  as  a  hydrate 
that  is,  chemically  combined  with  some  water  in  the 
form  of  a  delicate  blue  powder,  and  may  be  collected  on 
a  filter.     This  method  is  very  frequently  employed  for 
separating  metallic  oxides  from  metallic  salts. 

205.  Potassium  (K). 

If  the  oxygen  is  withdrawn  from  the  potassa,  then 
potassium  remains  behind,  — a  metal  which  has  so  strong 
a  tendency  to  combine  again  with  oxygen  that  it  can 
only  be  protected  against  oxidation  by  keeping  it  in 
petroleum,  a  liquid  which  contains  no  oxygen. 

The  usual  method   of    preparing   potassium   is "  by 

putting  carbonate  of  potas- 
sa  and  charcoal  into  an  iron 
vessel,  provided  with  an  iron 
exit-tube,  and  exposing  them 
to  the  strongest  white  heat. 
At  this  extremely  high  temperature,  the  coal  combines 
with  the  oxygen  of  the  carbonic  acid  and  of  the  po- 
tassa, forming  carbonic  oxide  gas,  which  escapes.  The 
liberated  potassium  is  also  converted  into  vapor,  which 
is  conducted  into  petroleum,  where  it  condenses  into  a 
solid  mass,  resembling  silver. 

It  has  been  shown  under  carbonic  acid  (§  166),  that 
potassium,  at  a  moderate  heat,  can  withdraw  the  oxy- 
gen from  the  carbon ;  while  here,  at  a  higher  temper- 
ature, the  contrary  takes  place.  Similar  incongruities 
in  chemical  actions  are  not  unfrequent ;  they  show  that 
the  affinities  of  bodies  for  each  other  are  greatly  altered 
by  the  temperature. 

Experiment.  —  Put  a  piece  of  potassium  of  the  size 
of  a  pea  into  a  basin  of  water  ;  it  floats  with  a  whizzing 
noise  upon  the  water,  and  burns  at  the  same  time  with 


POTASSIUM. 

a  lively  reddish  flame.  After  the  combustion  is  finished, 
the  potassium  has  apparently  vanished ;  but  it  is  in  fact 
in  solution  in  the  water,  being,  however,  no  longer  po- 
tassium, but  potassa,  as  we  may  easily  ascertain  by  red 
test-paper,  the  color  of  which  will  be  changed  by  the 
water  tq  blue.  Consequently  it  has,  during  the  com- 
bustion, combined  with  oxygen ;  this  oxygen  it  tock 
from  the  water,  and  so  much  heat  was  thereby  evolved 
that  the  second  constituent  of  the  water,  hydrogen,  was 
inflamed. 

If  a  piece  of  potassium  is  divided  with  a  knife,  it  pre- 
sents a  glistening  surface  like  silver ;  but  it  immediately 
tarnishes  on  exposure  to  the  moist  air,  and  soon  be- 
comes converted  into  a  white  body,  hydrate  of  potassa 
In  this  case  it  takes  the  oxygen  from  the  air. 

Salts  of  Potassa. 

Salts  are  produced,  as  has  been  before  stated,  when 
a  base  combines  with  an  oxygen  acid  or  a  hydrogen 
acid  (oxygen  salts  and  haloid  salts).  As  there  are 
hundreds  of  acids,  so  also  hundreds  of  potassa  salts  may 
be  prepared.  But  those  only  will  here  be  considered 
which  are  of  especial  importance  in  science,  the  arts,  or 
the  common  uses  of  life. 

206.   Sulphate  of  Potassa  (KO,  SO3). 
Dissolve  half  an  ounce  of  potash  in  two  ounces  of 
Fi«-  in          warm  water,  and  neutralize  with  diluted 
sulphuric    acid ;     evaporate    the    filtered 
liquid  till  a  film   appears  on  the  surface, 
then  let  it  remain  quiet  for  one  day.     The 
hard  crystals   obtained    (six-sided  double 
prisms)  are  sulphate  of  potassa ;  they  are 
sparingly  soluble  in  water,   and   have  a 
somewhat  bitter  taste.     This  salt  forms  a  constituent 
of  the  well-known  alum. 


226 


ALKALIES. 


Acid  Sulphate,  or  Bisulphate  of  Potassa  (KO,  2  SO 
-(-  HO)  is  obtained   as   a   secondary    product   in  the 
preparation   of  nitric  acid  from    saltpetre    (§159).     It 
contains  one  atom  of  base  and  two  atoms  of  acid,  and 
has  a  very  acid  taste.     But  the  second  atom  of  acid  is 
more  feebly  combined  than  the  first,  and  may  be  ex- 
pelled by  the  application  of  strong  heat. 
207.  Saltpetre,  Nitre,  or  Nitrate  of  Potassa  (KO,NO6). 
Dissolve  half  an  ounce   of  carbonate  of  po- 
Fig.  112.    tassa  jn  one  ounce  of  hot  water,  and  neutral- 
ize with  nitric  acid ;  afterwards  boil  and  filter 
the  liquid,  and  set  it  aside  to  cool ;  prismatic 
crystals    of   nitre    will  be   deposited    from    it. 
which    have  a  cooling   taste,  and  undergo  no 
alteiation  in  the  air. 
Experiments  with  Nitre. 

Experiment  a.  —  Heat  some  nitre  in  a  test-tube ;  it 
melts ;  if  you  pour  it  by  drops  upon  a  cold  stone,  you 
will  obtain  globules  of  nitre.  Upon  the  application  of 
a  stronger  heat,  oxygen  will  escape,  and  afterwards 
nitrogen ;  consequently,  the  nitric  acid  is  thereby  re- 
solved into  its  two  elements. 

Experiment  b.  —  If  you  throw  a  little  nitre  on  a  glow- 
ing coal,  it  will  sparkle  briskly ;  it  deflagrates.  In  this 
case,  also,  the  nitric  acid  is  decomposed,  and  its  sud- 
den conversion  into  two  gases  is  the  cause  of  the  spark- 
ling.  The  oxygen,  becoming  free,  finds  in  the  coal  a 
body  with  which  it  can  combine ;  the  escaping  gases 
are,  accordingly,  carbonic  acid  and  nitrogen.  A  portion 
of  the  carbonic  acid  formed  combines  with  the  potassa, 
which  remains  behind.  From  K  O,  N  O5,  and  2|  C  are 
formed  KO,  CO2,  and  \l  CO.,.  The  hard  saline  mass, 
congealed  from  its  molten  state,  remaining  on  the  coal 
has  a  basic  reaction,  and  effervesces  with  acids ;  it  is 


POTASSIUM. 


carbonate  of  potassa,  or  potash.  In  order  to  render  sub- 
stances more  inflammable,  they  are  often  drenched  with 
a  solution  of  nitre ;  as,  for  example,  tinder,  &c. 

Experiment  c.  —  Mix  thoroughly  in  a  mortar  six 
drachms  of  powdered  nitre,  one  drachm  of  charcoal- 
powder,  and  one  drachm  of  sulphur ;  this  is  pulver- 
ized gunpowder.  Take  a  little  on  the  point  of  a 
knife,  put  it  on  a  stone,  and  ignite  it  with  a  match;  a 
brisk  deflagration  will  ensue.  Knead  the  rest  of  the 
powder,  with  some  drops  of  water,  into  a  paste,  and 
squeeze  it  through  a  leaden  colander.  The  thread-like 
mass  thus  obtained  is,  when  partly  dry,  divided  by  gen- 
tly rubbing  with  the  fingers  into  small  grains ;  this  is 
gunpowder. 

Experiment  d. —  Place   some   gunpowder  upon   an 

iron  plate,  and  ignite  it; 
Volatile,  the  explosion  follows  even 
more  quickly  than  with 
the  pulverized  gunpow- 
der, because  the  granulat- 
ed gunpowder  is  less  com- 
pact than  the  pulverized. 
In  this,  as  in  the  former 
deflagration,  there  are  also  evolved  from  the  coal  and 
the  nitric  acid  carbonic  acid  and  nitrogen,  two  gases 
which  instantly  occupy  a  space  several  thousand  times 
greater  than  before.  Sulphur  riot  only  effects  an  easier 
ignition  of  the  gunpowder,  but  it  causes  also  a  strong- 
er evolution  of  gas;  since  it  combines  with  the  po- 
tassium of  the  nitre,  forming  sulphuret  of  potassium, 
whereby  three  atoms  of  free  carbonic  acid  are  evolved, 
while  in  experiment  b  (without  sulphur)  only  an 
atom  and  a  half  of  this  gas  has  been  set  free.  If 
the  deflagration  of  the  gunpowder  takes  place  in 


Voiatiie. 


2:28  ALKALIES. 

a  confined  space,  as  in  a  gun-barrel,  the  explosive  vio- 
lence with  which  the  two  gases  are  suddenly  expanded 
is  strong  enough  either  to  project  the  ball  or  to  burst 
the  gun.  The  sulphuret  of  potassium  remaining  on  the 
iron  gun-barrel  soon  becomes  moist  in  the  air,  and  then 
emits  the  odor  of  sulphuretted  hydrogen  (§  133) ;  at  the 
same  time,  the  iron  is  blackened  by  the  formation  of 
sulphuret  of  iron  upon  the  surface. 

Experiment  e.  —  Mix   twenty   grains  of   iron  filings 
with  ten  grains  of  nitre,  and 
heat  the  mixture  in  an  iron 
spoon,  the  handle  of  which 
has  been  fixed  into  a  cork; 
a  brisk  ignition  of  the  mix- 
ture will  ensue ;  the  iron  will 
be  oxidized  by  the  oxygen  of 
the    nitric    acid,    while    the 
nitrogen    escapes.     The    po- 
tassa  remaining  behind  may   be   dissolved  by  water. 
Nitre  is  on  this  account  well  adapted  for  converting 
metals  into  metallic  oxides. 

/.  —  If  nitre  be  heated  with  sulphuric  acid,  the  nitric 
acid  escapes  (§  159). 

g.  —  Animal  substances  are  preserved  from  putrefying 
by  nitre  ;  it  is  therefore  used  in  the  packing  of  meat. 

The  manufacture  of  nitre  is  conducted  in  a  very  pe- 
culiar manner.  Animal  substances,  for  instance,  pieces 
of  flesh,  hides,  hair,  &c.,  are  mixed  with  lime  and  earth, 
and  then  moistened  with  water  or  urine,  and  suffered 
to  putrefy  slowly.  Animal  substances  are  rich  in  nitro- 
gen, which,  during  putrefaction,  is  set  free  in  the  form 
of  ammonia  (NH3)  ;  this,  after  a  time,  unites  with  the 
oxygen  of  the  air,  forming  nitric  acid  (and  water),  which 
acid  is  immediately  neutralized  by  the  lime.  If  animal 


POTASSIUM.  229 

substances  decay  without  the  presence  of  lime,  or  some 
other  strong  base,  no  nitric  acid,  but  only  ammonia, 
will  be  produced;  consequently,  it  is  the  strong  base 
which  disposed  the  nitrogen  to  combine  with  the  oxygen 
(§  .146).  After  the  completion  of  the  putrefaction,  add 
water  to  extract  the  soluble  matter,  and  a  solution  of 
nitrate  of  lime  is  obtained,  which  is  converted  by  car- 
bonate of  potassa  into  soluble  nitrate  of  potassa,  arid 
insoluble  carbonate  of  lime.  Nitre-beds,  so  called,  are 
prepared  in  this  way.  We  also  obtain  nitre  from  the 
East  Indies,  where  it  is  spontaneously  generated  in 
many  limestones  containing  potassa.  • 

208.   Chlorate  of  Potassa  (KO,  Cl  O5). 

This  salt,  as  its  formula  indicates,  may  be  regarded 
as  a  brother  of  nitre ;  but  its  disposition,  compared  with 
that  of  the  latter,  is  far  more  intractable  and  violent, 
since  chloric  acid  is  much  more  easily  decomposed  than 
nitric  acid. 

Experiments  with  Chlorate  of  Potassa. 

Experiment  a.  —  Chlorate  of  potassa  is,  by  merely 
heating,  very  easily  resolved  into  oxygen  and  chloride 
of  potassium ;  therefore  it  is  used  in  the  preparation  of 
oxygen,  as  was  described  in  §  59. 

Experiment  b.  —  When  thrown  on  glowing  coals,  it 
deflagrates  still  more  briskly  than  nitre;  the  oxygen, 
as  it  is  liberated,  occasions  a  very  energetic  combustion 
of  the  coal.  This  salt  cannot  be  employed  in  the  prep- 
aration of  gunpowder,  as  the  rapidity  with  which  it 
explodes  would  be  too  much  for  the  guns ;  yet,  on  this 
very  account,  it  is  extremely  serviceable  in  fire-works, 
especially  for  producing  variegated  fires.  The  greatest 
caution  must  be  observed  in  pulverizing  and  mixing  it, 
as  it  may  explode  by  merely  rubbing  or  pounding  it. 
When  it  is  to  be  ground  fine,  it  should  always  be  previous- 
20  " 


ALKALIES. 

///  moistened  with  some  drops  of  water ;  the  mixing  of  it 
with  other  substances  must  always  be  done  with  the 
hand. 

Experiment  c.  —  Introduce  some  crystals  of  chlorate 
of  potassa  into  a  beaker-glass,  and  add  a  small  quan- 
tity of  alcohol,  and  afterwards  a  few  drops  of  sulphuric 
acid  ;  the  sulphuric  acid  expels  the  chloric  acid,  which 
is  immediately  decomposed,  and  there  is  so  great  an 
evolution  of  heat  as  to  inflame  the  alcohol. 

Experiment  d.  —  Mix  some  chlorate  of  potassa  be- 
tween the  fingers  with  about  half  as  much  flowers  ot 
sulphur,  and  throw  the  mixture  into  sulphuric  acid, 
contained  in  a  beaker-glass  ;  a  brisk  crackling  and  an 
ignition  of  the  sulphur  take  place.  This  experiment 
is  daily  performed,  though  in  a  somewhat  different  way, 
in  every  German  household,  although  not  exactly  with 
the  view  of  studying  chemistry.  Every  one  performs 
it  who  ignites  a  match  by  means  of  the  match-flask. 
The  red  mass  on  the  end  of  the  match  consists  of  chlo- 
rate of  potassa  and  sulphur,  which  has  been  colored  red 
by  cinnabar ;  and  the  flask  contains  asbestos,  moistened 
with  sulphuric  acid.  The  asbestos  serves  to  prevent 
the  too  deep  immersion  of  the  match.  10  parts  of  sul- 
phur, 8  of  sugar,  5  of  gum  Arabic,  2  of  cinnabar,  and  30 
of  finely  powdered  chlorate  of  potassa,  form  with  water 
a  good  inflammable  mass,  with  which  the  piece  of  wood 
previously  dipped  in  melted  sulphur  is  coated. 

e.  —  Chlorate  of  potassa,  like  nitre,  oxidizes  the  metals 
on  being  heated  with  them. 

/.  —  If  you  heat  chlorate  of  potassa  with  muriatic  acid, 
chlorine  escapes.  This  does  not  proceed,  however,  from 
the  chlorate  of  potassa,  but  from  the  muriatic  acid, 
which  is  deprived  of  its  hydrogen  by  the  oxygen  of  the 
chloric  acid,  in  the  same  manner  as  it  was  by  the  oxy« 
gen  of  the  manganese,  or  of  the  nitric  acid. 


POTASSIUM. 


231 


Easily 
soluble. 


Fig.  114. 


Chlorate  of  potassa  is  prepared  by  passing  chlorine 
into  a  hot  solution  of  potassa ;  the  process  is  illustrat- 
ed by  the  annexed  diagram :  two  salts  are  formed 
simultaneously,  chloride  of  potassium  and  chlorate  ol 

potassa ;  the  first  is  easi- 
Sparingiy   ly,  the  latter  more  spar- 

soluble.       .       i  i    -,-, 

mgly  soluble  in  water; 
they  may  therefore  be 
separated  from  each 
other  by  crystallization. 

Silicate  of  Potassa  is  the  principal  constituent  of 
most  rocks  and  of  glass  (§  204). 

209.  Chloride  of  Potassium,  or  Muriate  of  Potassa 
(KCl). 

Dissolve  half  an  ounce  of  carbonate  of  potassa  in 
water,  and  neutralize  with  muriatic  acid ; 
upon  concentrating  the  solution,  cubic 
crystals  will  be  obtained,  having  a  taste 
similar  to  common  salt.  They  consist  of 
potassium  and  chlorine,  and  if  dissolved  in 
water,  they  may  be  regarded  as  muriate  of 
potassa,  K  Cl  +  HO,  being  the  same  as  K O,  H Cl. 

210.  Iodide  of  Potassium,  or  Hydriodate  of  Potassa  (K  I). 

This  salt  likewise  crystallizes  in  cubes,  is  easily  sol- 
uble in  water,  and  is  employed  in  medicine  as  a  valu- 
able remedy. 

.  Experiment.  —  To  prove  that  iodine  is  really  con- 
tained in  this  white  salt,  heat  a  small  portion  of  it  in  a 
test-tube  with  a  little  manganese  and  some  drops  of 
sulphuric  acid,  when  violet  fumes  will  be  evolved.  If 
common  salt  is  treated  in  the  same  manner,  chlorine,  as 
is  known,  will  be  given  off.  The  chemical  action  is  the 
same  in  both  cases. 

211.  Tartar,  or  Bitartrate,  of  Potassa  (K  0, 2  T+  H  O) 
Common  sorrel,  the  branches  of  grape-vines,  unripe 


2f»2  ALKALIES. 

grapes,  &c.,  have  an  acid  taste ;  they  contain  an  acid 
a  115  salt,  tartar  (§  195).     These  plants 

absorb  the  alkali  from  the  soil,  but 
by  some  unknown  process  they 
prepare  the  tartaric  acid  by  means 
of  their  own  organization.  Ripe 
grapes  also  contain  tartaric  acid, 
but  the  sour  taste  is  concealed  in 
them  by  the  sweet  taste  of  sugar,  and  we  do  not  per- 
ceive it  until  the  sugar  is  converted  by  fermentation 
into  alcohol;  that  is,  until  the  must  is  converted  into 
wine.  A  great  part  of  the  tartar  is  deposited  in  the 
wine-casks  as  a  hard,  gray,  or  red  crust  (crude  tartar). 
When  this  is  purified  from  coloring  matter  by  recrys- 
tallization,  we  obtain  a  white  tartar  (purified  tartar). 
The  powder  of  it  is  well  known  under  the  name  of 
cream  of  tartar.  Tartar  is  very  sparingly  soluble  in 
water.  That  it  burns  on  heating,  forming  carbonate  of 
potassa,  has  been  already  shown  under  tartaric  acid. 
Pure  carbonate  of  potassa  is  commonly  prepared  from 
tartar. 

Neutral  Tartrate  of  Potassa  (K  O,  T). 
To  prepare  this  salt,  dissolve  half  an  ounce  of  pure 
carbonate  of  potassa  in  two  and  a  half  ounces  of  water, 
then  add  one  ounce  of  purified  tartar,  and  let  the  mix- 
ture stand  for  a  day  in  a  warm  place,  frequently  stirring 
it.  The  filtered  Uquid,  after  sufficient  evaporation, 
yields  prismatic  crystals,  or,  when  evaporated  to  dry- 
ness,  a  white  powder.  This  salt  is  very  easily  soluble, 
but  is  also  very  easily  decomposed  by  other  acids,  even 
by  very  feeble  ones.  On  mixing  a  solution  of  it  with 
vinegar,  a  white  powder,  cream  of  tartar,  is  precipitated. 
The  second  atom  of  the  base  is  very  easily  abstracted 
by  other  acids,  and  thus  the  sparingly  soluble  acid  salt 
tartar,  is  again  formed. 


POTASSIUM.  233 

As  in  the  above  experiment  the  second  atom  of  the 
acid  in  the  tartar  was  neutralized  by  potassa,  so  we  can 
also  neutralize  it  by  other  bases.  We  obtain  in  this 
manner  double  salts,  several  of  which  are  used  as  val- 
uable medicines. 
Tartrate  of*potasra  -}-  tartrate  of  water  =  cream  of  tartar. 

"       «        "  "  -f      "         "  soda  =  Rochelle  salts. 

"       "        "      -f-      "         "  ammonia  =  ammoniated  tartar. 

"       "         "      -j-      "         "  peroxide  of  iron        =  tartarized  iron. 

"       "        "      +      "         "  oxide  of  antimony  =  tartar  emetic. 

212.  Salt  of  Sorrel,  Acid  Oxalate,  or  Binoxalate  oj 
Potassa  (K  O,  2  C2  O3  +  2  H  O). 

The  leaves  of  the  wood-sorrel  have  a  sour  taste,  and 
contain  also  an  acid  salt,  the  base  of  which  is  likewise 
potassa  ;  the  acid,  howe'ver,  is  not  tartaric,  but  oxalic 
acid.  In  those  places  where  the  sorrel  grows  abun- 
dantly the  juice  is  expressed,  and  the  salt  is  obtained, 
by  evaporation  and  crystallization,  in  white,  sparingly 
soluble  crystals.  It  has  already  been  noticed  (§  197). 
It  is  in  common  use  for  removing  ink-spots  from  linen. 

213.  Liver  of  Sulphur,  or  Tersulphuret  of  Potassium 
(3KS3  +  KO,  S03). 

Experiment. —  Put  a  mixture  of  one  drachm  of  sulphur 
and  two  drachms  of  dry  carbonate  of  potassa  into  an 
iron  ladle  ;  cover  it  with  a  strip  of  sheet-iron,  and  heat 
it  until  the  effervescence  has  ceased  and  the  mass  flows 
quietly.  The  fused  mass  has  the  color  of  liver,  and  on 
this  account  has  received  the  name  liver  of  sulphur  ; 
pour  it  upon  a  stone,  and  if  it  should  inflame,  cover  it 
with  a  vessel  to  extinguish  it.  On  exposure  for  some 
time  to  the  air  it  becomes  greenish  and  moist,  and 
evolves  an  odor  like  that  of  rotten  eggs.  The  simple  sul- 
phur cannot  combine  directly  with  the  compound  car- 
bonate of  potassa,  but  it  can  do  so  if  the  latter  surrenders 
its  carbonic  acid  and  its  oxygen.  This  does  take  place 
20* 


234  ALKALIES. 

The  carbonic  acid  escapes  with  effervescence,  while  thv\ 
oxygen  combines  with  one  quarter  of  the  sulphur,  form- 
ing sulphuric  acid,  which  unites  with  a  portion  of  the 
undecomposed  potassa,  forming  sulphate  of  potassa , 
accordingly,  the  liver  of  sulphur  is  a  mixture  of  tersul- 
vim  ret  of  potassium  and  sulphate  of  potassa. 

Experiment.  —  Pour  water  into  a  test-tube  contain- 
ing some  liver  of  sulphur ;  you  obtain  a  yellowish- 
green  solution.  If  to  this  you  add  diluted  sulphuric 

acid,  a  strong  evolution 
Volatile,  of  sulphuretted  hydrogen 
takes  place,  and  the  liquid 
becomes  milky  from  the 
precipitation  of  two  thirds 

Soluble      °^  ^e   sulpnur    (milk   of 
sulphur).     A  decomposi- 

insoiubie.  tion  of  water  hereby  takes 
place ;  the  oxygen  of  the 
water  converts  the  potassium  into  potassa,  which  unites 
with  the  sulphuric  acid,  but  the  hydrogen  escapes,  with 
one  third  of  the  sulphur,  as  sulphuretted  hydrogen. 
The  same  thing  is  effected,  though  far  more  slowly,  by 
the  carbonic  acid  of  the  air,  and  thus  is  explained  why 
the  liver  of  sulphur  (as  well  as  the  residue  left  on  the 
combustion  of  gunpowder)  emits  a  smell  like  that  of 
rotten  eggs  when  it  is  left  exposed  to  the  air. 

The  liver  of  sulphur  is  chiefly  used  for  preparing  sul- 
phur baths.  A  similar  preparation  is  obtained  in  the 
moist  way,  as  has  been  described  (§  129). 

Besides  this  combination  of  potassium  with  sulphur, 
there  are  several  others,  containing  either  more  or  less 
sulphur.  The  simplest  compound  of  sulphur  and  potas- 
sium (KS)  is  obtained  by  heating  together  sulphate  of 
potassa  and  charcoal,  which  latter  abstracts  the  oxygen 


POTASSIUM.  23t5 

both  from  the  potassa  and  from  the  sulphuric  acid 
forming  with  it  carbonic  oxide,  which  escapes.  In  the 
same  manner  all  sulphates  are  converted  into  sulphur  eU 
by  heating  them  with  charcoal. 

214.  Potassa  Salts  as  Manure.  —  The  salts  of  potassa 
exercise  a  very  beneficial  influence  upon  the  fertility  of 
the  soil,  and  are  particularly  adapted  for  those  plants, 
in  the  ashes  of  which,  when  burnt,  the  potassa  salts  are 
found ;  namely,  for  the  grape-vine,  potatoes,  turnips,  &c. 
Such  plants  may  be  called  potassa  plants.  It  is  now 
known  that  plants  do  not  flourish  even  in  the  richest 
soil,  unless  they  find  in  it  certain  bases  (potassa,  lime, 
&c.),  and  also  certain  acids  (silicic,  phosphoric,  sul- 
phuric, &c.).  In  order  to  ascertain  what  acids  and 
bases,  or,  in  other  words,  what  salts,  are  required  for 
the  cultivation  of  a  certain  plant,  it  is  merely  necessary 
to  burn  this  plant  and  examine  the  ashes.  The  sub- 
stances which  are  found,  though  their  amount  is  gener- 
ally but  very  small,  must  be  regarded  as  indispensable 
to  the  nourishment  of  this  plant.  If  the  soil  is  destitute 
of  potassa,  neither  turnips  nor  grape-vines  will  flourish 
in  it ;  if  destitute  of  lime,  it  will  produce  neither  clover 
nor  peas.  By  the  addition  of  potassa  salts  we  can 
restore  to  such  a  soil  its  fertility  for  the  potassa  plants, 
and  by  the  addition  of  lime  we  again  render  it  produc- 
tive for  the  lime  plants.  On  this  is  founded  the  appli- 
cation of  the  so-called  mineral  manure  (lime,  gypsum, 
wood-ashes,  salt,  &c.)  to  our  fields.  Common  manure 
also,  and  soap-suds,  operate  partly  in  the  same  way 
since  they  are  rich  in  phosphoric  acid,  as  well  as  in  al- 
kaline and  in  lime  salts.  If  turnips  are  cultivated  sea- 
son after  season  upon  the  same  field,  the  potassa  will 
finally  become  exhausted,  and  turnips  will  no  longer 
grow  there;  the  same  thing  happens  when  peas  are 


236 


ALKALIES. 


planted  year  after  year  upon  the  same  land,  as  they 
will  at  last  exhaust  all  the  soluble  lime  from  the  soil. 
But  turnips  will  flourish  in  this  latter  field,  because  it 
still  contains  potassa,  and  peas  in  the  former  field, 
where  lime  is  still  present.  Thus  is  explained,  in  a  very 
simple  manner,  the  advantage  of  the  rotation  of  crops, 
which  has  been  universally  introduced  into  agriculture. 


x 


SODIUM  (Na). 
At.  Wt.  =  290.  — Sp.  Gr.  =  0.9. 

Common  Salt,  Chloride  of  Sodium,  or  Muriate  of  Soda 
(Na  Cl). 

215.  Experiment.  —  Dissolve  one  ounce  of  salt  in  two 
and  three  fourths  ounces  of  cold  water ;  the  water  will 
dissolve  no  more,  even  if  added.  Repeat  the  experi- 
ment, using  hot  instead  of  cold  water ;  the  result  is 
precisely  the  same.  'Common  salt  has  the  remarkable 
property  of  being'  equally  soluble  in  hot  and  in  cold 
water.  A  larger  quantity  of  almost  all  other  salts  is 
dissolved  by  hot  than  by  cold  water.  Put  one  of  these 
solutions  in  a  warm  place ;  by  the  gradual  evaporation, 
,  116  regular  transparent  crystals  of  common 
salt  are  formed.  Boil  down  the  other 
solution,  quickly  stirring  it  all  the  while ; 
it  yields  a  granular,  opaque,  saline  powder 
(disturbed  crystallization).  Salt  is  pre- 
pared as  last  described  on  a  large  scale 
and  hence  the  granular  state  of  common  salt. 

Experiment.  —  If  you  expose  a  solution  of  salt  in  an 
open  place  during  the  extreme  cold  of  winter,  transpar- 
ent prismatic  crystals  will  be  formed,  which  contain 
more  than  one  third  of  water.  When  placed  on  the 


SODIUM.  23? 

h  id  they  quickly  become  opaque  and  deliquesce  into 
a  syrupy  mass,  in  which  numerous  small  cubic  crys- 
tals may  be  perceived.  This  experiment  shows  very 
clearly,  — 

1.)  How  one  and  the  same  body  may  assume  differ- 
ent forms  at  ••different  temperatures ;  at  common  tem- 
peratures salt  crystallizes  in  anhydrous  cubes,  but  under 
the  influence  of  cold  in  hydrated  prisms. 

2.)  How  great  an  influence  temperature  exerts  upon 
the  affinities  of  bodies  for  each  other.  At  a  temper- 
ature above  the  freezing  point,  salt  has  no  affinity  for 
water ;  we  obtain  anhydrous  cubes  ;  below  the  freezing 
point  it  has  an  affinity  for  water,  and  we  obtain  prisms 
which  consist  of  a  chemical  combination  of  salt  and 
water. 

3.)  How  easily  chemical  bonds  of  affinity  may  be 
destroyed  again ;  the  heat  of  the  hand  even  is  sufficient 
to  destroy  the  affinity  of  salt  for  water. 

Experiment.  —  Heat  some  common  salt  on  a  plati- 
num foil;  it  will  snap  briskly,  and  part  of  it  will  be 
thrown  off  from  the  foil ;  that  which  remains  melts 
when  the  foil  becomes  red-hot.  The  snapping  proceeds 
from  a  trace  of  water  (water  of  decrepitation),  which 
has  remained  in  the  interstices  of  the  crystals  ;  on  being 
heated  it  expands  and  bursts  the  crystals  asunder. 

Salt  has  been  previously  twice  artificially  prepared ; 
namely,  once  from  sodium  and  chlorine  (§  153),  and 
again  from  soda  and  muriatic  acid  (§  186) ;  its  constit- 
uents are  accordingly  already  known.  It  has  the  formula 
Na  Cl.  If  water  is  present,  it  may  be  regarded  also  as 
muriate  of  soda,  for  Na  Cl  -f-  H  O  is  equal  to  Na  O, 
HC1. 

216.  The  earth  and  sea  abound  in  common  .salt ;  it 
may  therefore  be  easily  procured  in  large  quantities. 


238  ALKALIES. 

In  many  places  it  is  found  in  the  interior  of  the  earth, 
in  immense  beds,  from  which  it  is  broken  up  and 
dug  out.  This  salt  looks  like  a  transparent  stone, 
and  so  is  called  rock-salt.  In  those  places  where  the 
rock-salt  is  mixed  with  stones  and  earth,  a  hole  is 
bored  in  the  middle  of  the  bed,  and  water  is  let  into  it. 
The  water  is  pumped  out  again  as  soon  as  it  has  be- 
come saturated  with  the  salt,  and  is  again  expelled  by 
evaporation.  In  some  places  springs  are  found  contain- 
ing salt  in  solution,  the  so-called  natural  salt  springs. 
These  are  always  occasioned  by  the  water  permeating 
the  earth  over  a  bed  of  rock-salt,  and  appearing  as  a 
spring  at  some  lower  level. 

As  the  natural  springs  commonly  contain  much  more 
water  than  is  necessary  for  the  solution  of  the  salt,  a 
cheaper  method  than  that  of  fire,  namely,  a  current  of 
air,  is  first  employed  for  the  evaporation  of  it.  The 
salt  water  is  pumped  up  to  the  top  of  a  lofty  scaffold- 
ing filled  up  with  fagots  (graduation-house) ,  and  from 
which  it  is  made  to  fall  by  drops  through  the  fagots. 
It  diffuses  itself  over  the  branches,  and  thus  presents  a 
very  large  surface  to  the  air  passing  through,  whereby 
a  very  rapid  evaporation  is  effected.  All  natural  salt 
waters  contain  gypsum  in  solution ;  this  is  first  deposit- 
ed, since  it  is  difficultly  soluble,  and  encases  the  branch- 
es with  a  hard  crust.  When  the  greater  portion  of  the 
water  is  evaporated,  the  concentrated  brine  is  finally 
boiled  down  with  constant  stirring  in  large  pans,  and  the 
granular  salt,  which  separates,  is  raked  out  and  dried. 
During  the  evaporation,  a  solid  incrustation  is  deposited 
at  tiie  bottom  of  the  pans,  consisting  principally  of 
Glauber  salts  and  gypsum,  and  from  which  Glauber 
salts  are  extracted.  Finally,  a  somewhat  thick  liquid 
remains,  the  so-called  mother-water,  from  which  no 


SODIUM.  239 

more  salt  can  be  extracted ;  it  contains  the  easily 
soluble  foreign  salts  present  in  the  brine,  namely,  chlo- 
rides of  calcium  and  magnesium,  and  bromide  of  mag- 
nesium, and  is  used  for  baths  and  for  the  preparation 
of  bromine. 

In  hot -countries,  salt  is  also  prepared  from  sea-water, 
which  is  evaporated  in  shallow  tanks  by  the  heat  of  the 
sun.  It  is  called  bay-salt,  and  has  a  bitterish  taste,  ow- 
ing to  the  presence  of  salts  of  magnesia.  A  pound  of 
sea-water  contains  from  one  half  to  five  eighths  of  an 
ounce  of  common  salt. 

217.  Small  quantities  of  common  salt  are  found  in  al- 
most every  spring  of  water,  in  every  soil,  in  every  plant. 
Is  this  universal  diffusion  of  salt  to  be  regarded  as  acci- 
dental ?  By  no  means.  This  is  one  of  the  spiritual 
advantages  to  be  derived  from  the  study  of  the  natural 
sciences,  that  they  lead  us  to  distinguish,  in  the  wonder- 
ful arrangements  of  nature,  not  the  sport  of  chance,  but 
the  forming  hand  of  an  Eternal  Wisdom.  We  find 
common  salt  everywhere  in  nature,  because  it  is  indis- 
pensable to  the  life  of  animals  and  plants.  Without 
salt,  no  complete  digestion  of  food  could  take  place, 
and  therefore  we  justly  regard  it  as  a  universal  condi- 
ment. Animals  find  it  in  the  meat  and  plants  by 
which  they  are  nourished ;  plants  receive  it  from  the 
soil  and  rain,  and  it  is  well  known  that  we  can  promote 
the  fertility  of  our  fields  by  the  application  of  a  coarse 
kind  of  salt. 

Salt  is  also  used  for  preserving  animal  and  vegetable 
substances,  it  having  the  power  of  preventing  chemical 
decompositions,  or,  in  common  language,  putrefaction 
or  decay.  Meat  and  fish  are  salted  down,  and  wood 
for  the  purpose  of  building  is  rendered  more  durable  by 
being  impregnated  with  salt. 


240  ALKALIES. 

218.    Glauber  Salts,  or  Sulphate  of  Soda  (NaO,  S  O3  4 

10  HO). 

As  most  of  the  potassa  salts,  potassa,  and  potassium 
are  prepared  from  carbonate  of  potassa,  so  most  of  the 
soda  salts,  soda,  and  sodium  are  prepared  from  com- 
mon salt.  In  the  latter  case,  however,  an  in- 
direct process  must  often  be  resorted  to,  since 
chlorine  is  not  so  easily  removed  from  sodium 
as  carbonic  acid  is  from  potassa.  The  chloride 
of  sodium  must  first  be  converted  into  sulphate 
of  soda.  We  are  already  acquainted  with  this 
salt,  it  having  remained  in  the  retort  after  the 
preparation  of  muriatic  acid  (§  185),  where 
common  salt  was  heated  with  sulphuric  acid.  It  was 
formerly  taken  as  a  popular  medicine,  under  the  name 
of  Glauber  salts,  so  called  from  its  discoverer,  the  phy- 
sician, Glauber.  We  find  it  also  in  many  mineral 
waters,  for  instance,  in  the  Carlsbad  and  Pullna  waters, 
and  in  the  incrustation  of .  the  salt-pans,  as  was  men- 
tioned under  common  salt.  It  is  readily  soluble,  crys- 
tallizes in  four  or  six  sided  prisms,  and  has  a  nauseous 
bitter  taste. 

Experiment.  —  Place  half  an  ounce  of  transparent 
crystallized  Glauber  salts  in  a  warm  place ;  they  soon 
become  covered  with  an  opaque  white  coating,  and  final- 
ly crumble  into  powder;  they  effloresce.  The  powder 
obtained  weighs  hardly  a  quarter  of  an  ounce.  That 
which  was  lost  was  water.  Glauber  salts  contain  more 
than  half  their  weight  of  water  of  crystallization.  It  is 
thus  obvious  that  it  is  this  chemically  combined  water 
which  imparts  to  the  salt  its  form  and  transparency? 
both  of  which  are  lost  when  the  water  is  evaporated  by 
the  heat ;  but  they  reappear  when  the  pulverulent  an- 
hydrous salt  is  dissolved  in  boiling  water,  and  the  solu- 


SODIUM.  241 

tion  allowed  to  cool.  Carbonate  of  potassa  is  a  deli- 
quescent salt,  common  salt  is  a  permanent  salt  in  the  air, 
while  Glauber  salts  are  efflorescent.  Salts  which  efflo- 
resce must  be  kept  in  a  cool  place,  well  corked  up. 

Experiment.  —  If  a  crystal  of  Glauber  salts  is  heated 
on  charcoal  before  the  blow-pipe,  it  soon  melts,  because 
it  dissolves  in^its  water  of  crystallization  (watery  fu- 
sion) ;  it  becomes  dry  as  soon  as  the  water  is  expelled ; 
but  finally  it  melts  for  the  second  time  when  heated  to 
redness  (igneous  fusion).  Those  salts  which  contain 
no  water  of  crystallization  undergo  only  the  latter  kind 
of  fusion. 

Experiment.  —  Heat  in  a  small  flask  half  an  ounce  of 
water  to  33°  C.,  and  keep  it  at 
this  temperature,  gradually  add- 
ing  crystallized    Glauber  salts, 
as  long  as  they  are  dissolved, 
amounting  to  about  an  ounce 
and  a  half.     If  a  stronger  heat 
be  now  applied  to  the  saturated 
solution,   a   salt   will    separate 
(anhydrous  crystals) ;  if  you  let 
it  cool,  a  salt  will  likewise  sep- 
arate (hydrated  crystals) ;  —  fur- 
nishing another  example  of  the 
great  influence  exerted  by  tem- 
perature on  the  affinity  of  water  for  other  substances. 
Glauber  salts  have  the  peculiar  property  of  being  most 
soluble  in  water,  not  at  the  boiling  point,  but  at  a  lower 
temperature. 

Experiment.  —  If  you   dissolve  crystallized  Glauber 

salts  in  water,  cold  is  produced ;  but  if,  on  the  contrary, 

you  dissolve  anhydrous  Glauber  salts  in  water,  then  heat 

is  produced.     You  will  observe  exactly  the  same  phe- 

21 


242 


ALKALIES. 


nomena  if  you  perform  this  experiment  witn  carbonate 
of  soda,  taking  first  the  crystallized  and  then  the  cal- 
cined carbonate  of  soda.  Whence  the  source  of  this 
heat  ?  It  comes  from  the  water,  because  a  part  of  the 
water  combines  with  the  anhydrous  Glauber  salts,  or 
the  anhydrous  carbonate  of  soda,  as  water  of  crystalli- 
zation. Consequently,  it  is  a  phenomenon  very  similar 
to  that  which  takes  place  in  the  slaking  of  lime  (§  33). 

219.   Sulphuret  of  Sodium  (Na  S). 

Experiment.  —  Mix   a  small   portion   of  anhydrous 

Glauber  salts  with  a 
little  charcoal  powder, 
and  heat  the  mixture 
on  charcoal  before  the 
blow-pipe ;  they  will 
melt  with  brisk  effer- 
vescence into  a  brown 
mass,  which  dissolves 
in  water,  forming  a 
yellowish  liquid.  The 
coal,  when  heated  to 
redness,  abstracts  the 
oxygen  both  from  the 
soda  and  from  the  sul- 
phuric acid,  and  forms 
with  it  carbonic  oxide 
gas,  which  escapes  with 
effervescence ;  sodium 
and  sulphur  remain  be- 
hind, combined  with  each  other.  That  is,  the  coal  de- 
oxidizes the  sulphate  of  soda,  or  reduces  it  to  sulphuret 
of  sodium. 

If  you  drop  muriatic  or  diluted  sulphuric  acid  into 


Volatile. 


SODIUM. 


Volatile, 


the   solution,    the 
agreeable       smell      01 
sulphuretted    hydrogen 
will  be  given  off,  just 
as  in  the  case   of  liver 
of  sulphur  (§£15).     If  you  now  let  the  liquid  evapo 
rate  on  a  glass  plate,  you  obtain,  in  the  former  case 
small  cubes  of  common  salt,  and  in  the  latter,  a  pul 
vemlent  incrustation  of  Glauber  salts. 

220.   Carbonate  of  Soda  (Na  O,  C  O,  +  10  H  O). 

Experiment.  —  Prepare  some  more  sulphuret  of  sodi- 
um in  the  manner  just  described,  rub  it  in  a  mortar 
with  the  adhering  particles  of  charcoal  and  with  about 
its  own  weight  of  chalk,  and  ignite  it  again  before 
the  blow-pipe.  Boil  the  baked  saline  mass  in  water, 
and  then  filter  the  liquid.  A  gray  powder  remains 
behind,  which,  when  drenched  with  muriatic  acid, 
evolves  sulphuretted  hydrogen  ;  it  is  sulphuret  of  cal- 
cium. The  liquid,  after  being  evaporated  on  a  shallow 
glass  dish,  leaves  behind  a  white  powder,  which  has  an 
alkaline  reaction  and  effervesces  with  muriatic  acid, 
but  yet  without  emitting  any  disagreeable  odor  ;  it  is 

carbonate  of  soda.  The 
sulphur  has  thus  passed 
to  the  calcium  of  the 
soluble,  chalk,  while  the  oxygen 
and  the  carbonic  acid 
of  the  chalk  have  passed  to  the  sodium.  By  these 
processes  it  will  be  seen  that,  as  in  the  daily  affairs 
of  life,  so  also  in  chemistry,  we  can  often  obtain  indi 
rectly  that  which  could  not  be  gained  directly.  So- 
dium has  a  stronger  affinity  for  chlorine  than  for  oxy 
gen  ;  therefore  we  cannot  prepare  soda  directly  frorr 


244 


ALKALIES. 


common  salt ;  but  by  means  of  sulphuric  acid  we  can 
easily  convert  the  haloid  salt  into  an  oxy-salt,  —  into 
sulphate  of  soda.  The  strong  sulphuric  acid  cannot  be 
directly  expelled  from  this;  we  therefore  first  decompose 
it  into  oxygen  and  sulphur,  and  afterwards  remove  the 
sulphur  by  another  metal,  calcium,  which  forms  with 
sulphur  an  insoluble  compound.  Soda  is  thus  obtained, 
yet  not  in  a  free  state,  but  as  carbonate  of  soda;  car- 
bonic acid,  however,  is  so  feeble  an  acid,  that  it  may 
easily  be  expelled  by  another  acid,  or  by  caustic  lime. 

As  carbonate  of  soda  possesses  almost  the  same 
properties  as  carbonate  of  potassa,  and  may  be  advan- 
tageously employed  instead  of  the  latter  in  washing 
and  bleaching,  and  also  in  the  manufacture  of  glass 
and  soap,  it  is  now  manufactured  on  a  large  scale  in 
chemical  works.  There  are,  in  Germany,  laboratories 
where  from  ten  to  twelve  thousand  quintals  of  soda  are 
annually  made.  The  process  pursued  is  essentially  the 
same  as  that  already  described,  except  that  the  two 

operations,  described  as 
separate  above,  are  unit- 
ed into  one ;  the  chalk  or 
1  limestone  is  added,  in  the 
first  place,  to  the  Glau- 
ber salts  and  charcoal, 
and  the  whole  mass  is 
heated.  This  is  done  in 
a  large  oven-shaped  fur- 
nace, represented  in  the 
figure,  a  is  the  grate,  b 
the  ash-pit,  p  the  chim- 
ney, d  d  the  hearth  for 
receiving  the  mixture,  t 
the  aperture  for  throwing  in  the  mixure,  and  g  an  open- 


SODIUM. 

ing  for  stirring  it  and  scooping  it  out.  They  are  called 
flame-furnaces,  because  the  heating  is  effected,  not  by 
the  fuel  itself,  but  by  the  flame  passing  over  the  bridge 
c ;  they  possess  this  important  advantage,  that  the 
ashes  of  the  pit-coal  or  peat  do  not  become  mixed 
with  the*  substance  to  be  heated.  In  many  countries 
an  impure  soda  is  also  obtained  from  the  ashes  of 
marine  plants  (kelp). 

Carbonate  of  soda  consists  of  equal  atoms  of  soda 
and  carbonic  acid.  It  occurs  in  commerce,  either  crys- 
tallized, —  it  then  contains  more  than  half  its  weight  of 
water  of  crystallization  (10  atoms)  and  effloresces 
very  readily,  —  or  calcined,  consequently  anhydrous. 
The  latter,  accordingly,  when  it  occurs  pure,  is  of  more 
than  twice  the  strength  of  the  crystallized.  Carbonate 
of  soda  is  easily  soluble  in  water.  Many  mineral  wa- 
ters—  for  example,  the  Carlsbad  springs — contain  great 
quantities  of  it  in  solution ;  Carlsbad  salt,  obtained  by 
evaporating  the  waters  of  the  spring,  is  a  mixture  of 
carbonate  and  sulphate  of  soda. 

Bicarbonate  of  Soda  (NaO,  2CO2  +  HO) 

is  more  sparingly  soluble  than  the  former  salt,  and  is 
frequently  used  in  effervescing  powders,  because  it 
evolves  on  being  mixed  with  acids  as  much  again  car- 
bonic acid  as  the  simple  carbonate.  Effervescing  pow- 
ders are  prepared  by  triturating  together  equal  portions 
of  tartaric  acid  and  bicarbonate  of  soda.  If  you  put 
this  mixture  into  water,  tartrate  of  soda  is  formed,  and 
carbonic  acid  escapes:  When  heated,  this  salt  com- 
ports itself  like  the  bicarbonate  of  potassa. 

221.  Soda,  or  Oxide  of  Sodium  (Na  O). 

If  you  take  from  the  carbonate  of  soda  its  carbonia 
21* 


246 


AL.KALIES. 


acid,  soda  will  remain  behind.  This  is  done  by  boiling 
a  solution  of  soda  with  quicklime,  in  the  same  manner 
as  was  described  under  potassa  (§  203).  The  liquid 
thus  obtained  is  called  caustic  soda  lye,  and  yields,  after 
evaporation,  caustic  soda.  This  contains,  like  caustic 
potassa,  yet  one  atom  of  water,  which  it  does  not  part 
with  even  when  heated  to  redness ;  hence  it  has  been 
more  correctly  called  hydrate  of  soda  (Na  O,  HO).' 
The  hydrate  of  soda  has  a  corrosive  action,  forms  soap 
with  fat,  and  hard  glass  when  melted  with  sand ;  it  is  a 
very  strong  base,  like  caustic  potassa,  for  which  it  is 
often  substituted  in  preference  in  the  arts. 

222.   Sodium  (Na). 

On  abstracting  oxygen  from  the  soda  metallic  sodium 
is  obtained.  This  metal  is  prepared  like  potassium, 
which  it  greatly  resembles,  though  it  does  not  act  so 
violently  upon  other  bodies,  for  instance,  upon  water. 
Put  upon  cold  water,  it  oxidizes  without  flame,  but  put 
upon  hot  water,  the  escaping  hydrogen  ignites,  and 
burns  with  a  yellow  flame. 

We  have  now  passed  from  the  most  widely  diffused 
common  salt  to  the  element  sodium,  treating  each  one 
in  that  succession  which  it  is  necessary  to  pursue  in  the 
actual  preparation  of  these  substances.  The  following 
summary  statement  may  serve  to  fix  them  on  the  mem- 
ory :  —  From  common  salt,  or  chloride  of  sodium,  sul- 
phate of  soda  is  prepared ;  from  this,  sulphuret  of  so- 
dium ;  from  this,  carbonate  of  soda ;  then  soda ;  and 
fina  ly  sodium. 

A  few  other  salts  of  soda  will  now  be  considered. 

223.  Phosphate  of  Soda. 
Experiment.-—  Neutralize  half  an  ounce  of  carbonate 


SODIUM. 


247 


Fig.  121. 


of  soda,  dissolved  in  water,  with  phosphoric  acid  pre- 
pared from  bones  ;  filter  the  liquid  from  the  phosphate 
of  lime  which  separates,  and  evaporate  the  filtrate  until 
a  film  forms  on  the  surface ;  on  cooling,  transparent 
crystals  will  be  deposited,  which  contain  more  than  half 
their  weight  of  water  of  crystallization.  They  easily 
effloresce,  ancf'yield  a  yellow  precipitate,  with  a 'solution 
of  nitrate  of  silver. 

Experiment.  —  Let  some  of  the  crystals  of  the  phos- 
phate of  soda  effloresce  in  a  warm 
place,  and  afterwards  heat  them 
to  redness  in  a  porcelain  crucible. 
When  the  mass  is  cold,  dissolve  it  in 
water,  and  evaporate  the  solution; 
you  obtain  a  salt  which  contains  far 
less  water  of  crystallization  than  the 
former  one ;  it  no  longer  effloresces, 
and  yields  with  nitrate  of  silver  a  white  precipitate ;  it 
has  received  the  name  of  pyrophosphate  of  soda.  This 
example  shows  how  the  affinity  of  a  salt  for  water  may 
be  weakened  by  being  heated  to  redness,  and  how  the 
properties  of  a  salt  may  be  changed,  according  to  the 
amount  of  water  with  which  it  is  chemically  united. 

224.  Nitrate  of  Soda  (NaO,  NO6). 

Experiment.  —  Dissolve  half  an  ounce  of  carbonate 
of  soda  in  a  little  hot  water,  and  neutral- 
ize it  with  nitric  acid  ;  then  evaporate  the 
solution  till  a  pellicle  begins  to  form, 
when  crystals  will  separate,  having  the 
form  of  an  oblique  rhombic  prism ;  they 
are  nitrate  of  soda.  They  deflagrate  on  charcoal  like 
nitrate  of  potassa,  onl}  somewhat  less  violently,  and 
have  the  greatest  similarity  to  it  in  other  respects. 


Fig.  122. 


248  ALKALIES. 

Large  districts  of  this  salt  are  found  in  America,  whence 
whole  ship-loads  of  it  are  exported,  under  the  name  of 
Chili  saltpetre  ;  and  it  is  substituted  for  the  more  costly 
nitre  in  the  manufacture  of  nitric  acid  and  some  of  its 
salts.  But  it  does  not  answer  for  making  gunpowder, 
as  the  powder  thus  prepared  becomes  moist,  and  deto- 
nates too  slowly. 

225.  Biborate  of  Soda  (Borax)  (Na  0, 2  B  O3  +  10  H  O). 

The  hard,  colorless  crystals  commonly  called  borax, 
and  generally  covered  with  an  efflorescent  powder,  con- 
sist of  soda  and  boracic  acid.  Boracic  acid,  in  the 
moist  condition,  is  a  feeble  acid ;  therefore,  like  carbonic 
acid,  it  cannot  entirely  conceal  the  basic  properties  of 
soda ;  and  borax  has  an  alkaline  taste,  and  colors  red 
test-paper  blue.  Borax  contains  half  its  weight  of  wa- 
ter of  crystallization. 

Experiment.  —  Heat  some  powdered  borax  upon  a 
platinum  wire  before  the  blow-pipe ;  it  will  puff  up  and 
swell  in  its  water  of  crystallization,  and  be  converted 
into  a  porous  spongy  mass ;  on  being  further  heated,  it 
fuses  to  a  transparent  bead.  Moisten  this  bead  with 
the  tongue,  apply  it  to  litharge  so  that  some  of  the  lat- 
ter may  adhere  to  it,  and  again  hold  it  in  the  exterior 
flame  of  the  blow-pipe ;  the  litharge  is  dissolved ;  the 
bead  remains  colorless  and  transparent.  If  you  now 
substitute  for  the  litharge  other  metallic  oxides,  you  will 
likewise  observe  that  the  oxides  will  dissolve,  but  that  at 
the  same  time  the  bead  will  be  colored  by  them ;  namely, 
yellowish-red,  by  sesquioxide  of  iron  and  oxide  of  anti- 
mony ;  green,  by  the  oxides  of  copper  and  chromium ; 
blue,  by  oxide  of  cobalt ;  violet,  by  a  small  portion  of 
oxide  of  manganese ;  and  brownish-black,  by  an  excess 
of  manganese.  The  metallic  oxides  comport  themselves 


SODIUM. 

also  iii  the  same  manner,  when  they  are  fused  into 
common  glass  or  earthen  ware.  They  are  for  this  rea- 
son called  vitriftable  pigments  (borates  or  silicates  of 
metallic  oxides). 

On  account  of  this  property  which  borax  has  of  dis- 
solving, metallic  oxides,  it  is  used  in  chemistry  as  a 
blow-pipe  test  for  the  detection  of  metallic  oxides,  and 
in  the  trades  for  soldering^  or  joining  one  metal  with 
another. 

Hold  by  the  forceps  a  piece  of  copper,  on  which  is 

placed  a  piece  of  tin  and 

Fig.  123. 

iron  wire,  over  the  name  01 
a  spirit-lamp ;  the  tin  will 
indeed  melt,  but  it  will  not 
adhere  either  to  the  copper 
or  the  iron.  Repeat  the  ex- 
periment, having  previously 
smeared  the  copper  and  the 

wire  with  a  paste  ,  made  of  borax-powder  and  water ; 
the  result  is  now  quite  different,  for  the  melting  tin 
unites  with  both  metals,  and  the  wire,  when  cold,  is 
found  to  be  firmly  soldered  upon  the  copper.  The 
explanation  of  this  different  result  is  simply  as  fol- 
lows. Metals  only  adhere  to  metals  when  they  have 
clean,  polished  surfaces ;  the  clean  surface  is  lost  on 
heating  the  metals,  because  a  layer  of  oxide  is  formed 
upon  them  by  the  oxygen  of  the  air ;  but  the  bright  sur- 
face is  restored  again  by  the  borax,  which,  when  it 
melts,  dissolves  the  oxide  formed. 

Borax  occurs  native  (tincal)  in  many  of  the  lakes  of 
Asia;  but  it  is  now  prepared  also  from  boracic  acid, 
which  is  obtained  from  some  hot  springs  in  Italy,  and 
is  neutralized  by  soda. 


250  ALKALIES. 

226.   Glass  (Silicic  Acid  combined  with  Bases). 

As  boracic  acid  'forms  with  soda,  when  heated,  a  vit* 
reous  compound,  so  silicic  acid,  which  is  very  analogous 
to  boracic  acid,  forms  likewise  a  vitreous  combination 
with  soda,  and  also  with  other  bases,  as  with  potassa, 
lime,  oxide  of  lead,  oxide  of  iron,  &c.  Glass,  glazing, 
enamel,  &c.,  are  varieties  of  this  combination. 

Experiment.  —  Melt  some  carbonate  of  potassa  or 
soda  upon  a  platinum  wire  before  the  blow-pipe,  and 
then  add  a  little  finely  pulverized  sand ;  upon  placing 
it  again  in  the  blow-pipe  flame,  effervescence  will  ensue, 
and  afterwards  a,  clear  bead  will  be  formed.  If  the 
proportion  of  sand  used  be  small,  the  glass  formed  (basic 
silicate  of  potassa  or  soda)  will  dissolve  in  water  on 
long-continued  boiling;  it  is  then  called  soluble  glass 
(§204).  If  more  sand  is  taken,  a  glass  (acid  silicate  of 
potassa  or  soda)  is  obtained  which  it  is  very  difficult 
to  dissolve  in  water.  To  make  a  glass  which  shall 
be  entirely  insoluble,  not  only  in  water  but  also  in 
acids,  beside  the  potassa  and  soda,  some  other  earth  or 
metallic  base  —  for  instance,  lime  or  litharge  —  must  be 
added.  Common  £lass  is  thus  manufactured  in  glass- 
houses. 

The  materials  which  are  chiefly  employed  in  the 
manufacture  of  glass  are,  —  a)  quartz,  flint,  or  sand; 
b)  carbonate  of  potassa  or  wood-ashes;  c)  carbonate  of- 
soda  or  Glauber  salts ;  d)  lime  or  chalk ;  e)  litharge  or 
minium.  These  substances,  after  being  pulverized,  are 
mixed  together,  thrown  into  earthen  pots,  and  heated 
in  a  furnace  until  the  mass  •  is  one  uniform  fluid.  In 
this  state  it  may  be  moulded  like  wax,  cut  and  bent, 
pressed  into  moulds,  and  blown,  and  may  accordingly 
be  manufactured  into  all  possible  shapes  and  forms ;  on 


cooling,  it  becomes  hard  and  brittle.  In  order  to  di 
minish  in  a  measure  the  brittleness,  the  glass  must  be 
cooled  very  slowly  (annealed).  Glass  vessels  that  are 
rapidly  cooled  often  crack  when  they  are  carried  from 
a  warm  into  a  cold  room ;  this  defect  may,  to  a  certain 
degree,  t>e  cgrrected^by  gradually  heating  the  vessels  in 
water  till  it  boils,  and  then  allowing  it  to  cool  very 
slowly. 

For  coloring  and  painting  glass  the  vitrifiable  pig- 
ments, as  noticed  in  §  225,  are  employed.  The  milk- 
white  color  which  we  observe  in  the  opaque  glass  of 
the  lamp-screens,  and  in  the  enamel  of  the  dial-plate  of 
watches,  is  produced  by  finely  ground  bone-earth  or 
oxide  of  tin,  neither  of  which  substances  is  dissolved  by 
the  vitreous  mass,  but  only  mixes  with  it  mechanically, 
and  renders  it  opaque,  as  chalk  does  "water.  Glass  is 
ground  by  sand  and  emery,  polished  by  sesquioxide  of 
iron  and  tripoli,  etched  by  hydrofluoric  acid,  and  very 
.  easily  perforated  by  the  point  of  a  three-cornered  file, 
which  should  be  frequently  moistened  with  oil  of  tur- 
pentine. 

The  two  principal  kinds  of  glass  are,  — 

a)  Crown  or  Bohemian  glass,  consisting  of  potassa 
(soda),  lime,  and  silica. 

b)  Flint  or  crystal  glass,  consisting  of  potassa,  oxide 
of  lead,  and  silica. 

Common  bottle-glass  contains  the  same  ingredients 
as  crown  glass,  with  the  addition  of  sesquioxide  ol 
iron,  which  imparts  to  it  a  brownish-yellow  color,  or  of 
protoxide  of  iron,  which  gives  it  a  green  tinge.  This 
iron  is  contained  in  the  impure  materials  (yellow  sand 
and  wood-ashes)  used  in  the  preparation  of  the  ordinary 
sorts  of  glass. 


252 


ALKALIES. 


SYSTEMATIC   ARRANGEMENT    OF    THE    COMPOUNDS  OF 
POTASSIUM  AND  SODIUM. 


Metals:         Potassium. 
Oxides :         Oxide  of  potassium,  or  caus- 
tic potassa. 
Sulphurets:    Sulphuret  of  potassium,  or 

Liver  of  sulphur. 
Haloid  Salts :  Chloride  of  potassium. 

Iodide  of  potassium. 
Oxy-salts :      Carbonate  of  potassa. 
Bicarbonate  of  potassa. 
Chlorate  of  potassa. 
Nitrate  of  potassa,  or  salt- 
petre. 
Sulphate  o£  potassa. 

Bisulphate  of  potassa 

Silicate  of  potassa,  or  glass. 
Basic  silicate  of  potassa,  or 

soluble  glass. 
Tartrate  of  potassa. 
Bitartrate  of  potassa,  or  tartar. 
Double  salts  of  tartar. 
Binoxalate  of  potassa,  or  salt 

of  sorrel. 
Acetate  of  potassa,  &c. 


Sodium. 

Oxide  of  sodium,  or  caustic 

soda. 
Sulphuret  of  sodium. 

Chloride  of  sodium. 
Iodide  of  sodium. 
Carbonate  of  soda. 
Bicarbonate  of  soda. 

Nitrate  of  soda,  or  Chili  salt- 
petre. 

Sulphate  of  soda,  or  Glaubef 
salts. 

Bisulphate  of  soda. 

Sulphite  of  soda. 

Phosphate  of  soda. 

Silicate  of  soda,  or  glass. 

Biborate  of  soda,  or  borax. 


AMMONIA  (NH3). 
At.  Wt.  =  213.  —  Sp.  Gr.  [as  gas]  =  0.6. 

227.  Experiment.  —  1.)  Mix  intimately  together  forty 
grains  of  fine  iron  filings,  and  two  grains  of  hydrate  of 
potassa  (caustic  potassa),  and  heat  them  in  a  test-tube, 
to  which  is  adapted  a  bent  glass  tube  (Fig.  26).  As 
soon  as  the  atmospheric  air  is  expelled,  receive  the  gas 
as  it  is  evolved  in  a  separate  flask ;  it  may  be  inflamed 


AMMO  XT  A. 


253 


Volatile. 


by  a  lighted  taper  ;  it  is  hydrogen.     It  comes  from  the 
water  of  the  hydrate  of  potassa,  the  oxygen  of  which 

combines  with  the  iron. 
Volatile.     The  potassa  serves  to 
hold  fast  the  water,  un- 
Soiubie.      til    a  red  heat   is  pro- 
duced :  water,  by  itself, 

Insoluble 

only  to  100°  C. 

Experiment.  —  2.)  Heat  forty  grains  of  iron  filings  and 
two  grains  of  nitre  in  the  same  manner  as  before.    You 

obtain  a  gas  in  which  a 
lighted  taper  is  extin- 
guished; it  is  nitrogen. 
The  same  occurs  in 
the  case  of  nitric  acid 
as  with  the  water;  the 
iron  abstracts  from  it 
oxygen  ;  and  its  second  constituent,  nitrogen,  is  thereby 
set  free,  and  escapes. 

Experiment.  —  3.)  Unite  the  two  former  experiments 

into  one,  that  is,  heat 
eighty  grains  of  iron 
Volatile,  filings  at  the  same  time 
with  two  grains  of  po- 
Non.  tassa  and  two  grains 
of  nitre,  in  an  open 
test-tube :  neither  hy- 
drogen nor  nitrogen  is 
evolved,  but  a  combination  of  both  in  a  gaseous  form, 
having  a  pungent  odor  resembling  that  of  ammonia. 
A  strip  of  moistened  red  test-paper  held  over  the  test- 
tube  is  turned  blue ;  consequently,  this  new  kind  of  gas 
possesses  an  alkaline  character ;  we  call  it  ammonia. 
22 


volatile. 


254 


ALKALIES, 


Ammonia  is,  as  we  see,  a  chemical  combination  of  hy- 
drogen and  nitrogen.  But  these  two  bodies  unite  with 
each  other  only  at  the  moment  of  being  liberated  from 
another  combination  (nascent  state).  If  they  do  not 
come  together  till  afterwards,  when  they  have  already 
become  gaseous,  no  union  takes  place. 

In  ammonia,  one  atom  of  nitrogen  is  always  com- 
bined with  three  atoms  of  hydrogen ;  therefore  its  formu- 
la is  NH3.  From  three  measures  of  hydrogen  and  one 
measure  of  nitrogen  are  formed,  not  four  measures,  but 
only  two  measures,  of  ammoniacal  gas ;  accordingly, 
the  ammoniacal  gas  occupies  only  half  the  space  previ- 
ously occupied  by  its  constituents,  and  a  condensation 
of  one  half  is  produced  by  chemical  combination.  In 
the  formation  of  water  from  its  constituents,  this  con- 
densation amounted  to  two  thirds  (§  87). 

228.  Ammonia  by  dry  Distillation.  —  Ammonia  is  also 
produced  when  animal  substances  are  heated  with  ex- 
clusion of  air.  These  substances  always  contain  nitro- 
gen and  hydrogen,  which,  at  the  moment  of  being  set 
free  by  heat,  combine  with  each  other,  forming  am- 
monia. 

Experiment.  —  Reduce  to  a  coarse  powder  one  ounce 

Fig.  124. 


AMMONIA.  250 

of  bones,  and  heat  them  in  a  flask  as  long  as  any  vola- 
tile matter  continues  to  escape.  The  flask  must  be 
previously  connected,  by  a  bent  glass  tube,  with  a  bottle 
containing  a  little  water,  which  bottle  must  be  kept  cool 
in  a  basin  of  water.  Adapt  to  the  cork  of  the  receiving 
bottle  another  glass  tube  open  at  both  ends,  through 
which  those  gases  may  escape  which  are  not  absorbed 
by  the  water.  These  smell  very  disagreeably,  but  the 
odor  vanishes  when  they  are  inflamed.  The  gases  burn 
with  a  luminous  flame,  like  pit-coal  gas,  which  they 
much  resemble  in  their  constitution.  A  brownish-black 
tarry  matter  is  deposited  in  the  bottle,  which  is  known 
under  the  name  of  oil  of  hartshorn,  or  Dippell's  ani- 
mal oil.  After  the  completion  of  the  dry  distillation, 
it  is  separated  from  the  watery  solution  by  filtering 
through  paper  previously  moistened  with  water.  The 
filtrate  still  contains  some  of  this  oil  in  solution,  and  has 
thereby  a  brown  color  and  an  agreeable  odor.  But  at 
the  same  time  we  perceive  also  a  pungent  smell  of  am- 
monia,  which  latter  is  also  detected  by  means  of  red 
test-paper,  the  color  of  which  is  changed  to  blue. 

Add  some  lime-water  to  this  ammoniacal  solution ; 
it  becomes  turbid,  and  emits  a  more  powerful  odor  of 
ammonia.  The  turbidness  is  owing  to  the  precipita- 
tion of  carbonate  of  lime,  the  ammonia  not  being  free 
in  the  liquid,  but  combined  with  carbonic  acid.  Car- 
bonic acid  is  generated  during  every  combustion  or 
charring  of  organic  substances ;  it  here  finds  a  base  in 
the  ammonia,  and  consequently  combines  with  it.  In 
the  carbonate  of  potassa  and  carbonate  of  soda,  we 
have  already  seen  that  the  basic  properties  of  the  po- 
tassa and  of  the  soda  are  not  entirely  concealed  by  the 
carbonic  acid,  —  that  the  base,  as  it  were,  still  glimmers 
through.  Ammonia  also  comports  itself  quite  in  th? 


256 


ALKALIES. 


same  manner;  although  chemically  combined  with 
carbonic  acid,  it  still  emits  a  pungent  odor,  and  affords 
an  alkaline  or  basic  reaction.  Formerly  this  pungent 
brown  liquid  was  used  as  a  popular  sudorific,  and  was 
called  spirit  of  hartshorn,  because  it  was  prepared  from 
harts'  horns,  instead  of  from  bones."  For  the  same  rea- 
son, the  impure  dry  carbonate  of  ammonia  prepared  from 
it  received  the  name,  still  in  use,  of  salt  of  hartshorn. 

It  is  only  with  difficulty  that  this  pungent  oil  can  be 
separated  from  the  carbonate  of  ammonia ;  this  separa- 
tion is  most  easily  effected  by  converting  the  carbonate 
of  ammonia  into  chloride  of  ammonium. 

Sal  Ammoniac,  or  Chloride  of  Ammonium  (N  H3,  H  Cl). 

229.  Experiment.  —  Neutralize  the  ammoniacal  liquid 
obtained  in  the  last  experiment  with  muriatic  acid ;  boil 
it  with  some  animal  charcoal,  and  filter  it.  After  fil- 
tration, the  liquid  has  less  color  than  before,  because  a 
great  part  of  the  coloring  matter  has  been  absorbed  by 
the  coal  (§  105) ;  after  sufficient  evaporation  it  yields 
brown  crystals,  which  are  finally  rendered  entirely  col- 
orless by  repeated  solution  and  boiling  with  coal.  This 
salt  was  formerly  prepared  in  the  district  of  Ammonia, 
in  Africa,  from  camel's  dung ;  hence  its  name,  sal  am- 
moniac. The  ammonia  in  this,  as  in  its  other  salts,  is 
so  completely  neutralized  by  the  acids,  that  you  can 
no  longer  recognize  it  by  the  smell. 

Experiments  with  Sal  Ammoniac. 

Experiment  a.  —  If  some  sal  ammoniac  is  heated 
upon  a  platinum  foil,  over  the  flame  of  a  spirit-lamp,  it 
volatilizes  in  white  fumes.  All  ammoniacal  salts  are 
volatilized  by  heat.  If  the  vapor  of  sal  ammoniac  is 
condensed  in  a  cold  vessel,  you  obtain  it  as  a  solid, 


AMMONIA.  257 

transparent  mass,  which  is  pulverized  with  difficulty 
The  sal  ammoniac  of  commerce  generally  occurs  in  this 
form ;  it  is  then  called  sublimed  sal  ammoniac. 

Experiment  b.  —  Throw  some  powdered  sal  ammo- 
niac into  water  in  which  a  thermometer  is  immersed; 
the  powder  ^readily  dissolves,  and  the  mercury  falls 
considerably.  In  this  manner,  artificial  cold  may  be 
produced. 

Experiment  c.  — -If  sal  ammoniac  is  triturated  with 
slaked  lime  or  potassa,  it  evolves  a  strong  ammoniacal 
odor,  because  the  potassa  or  the  lime  abstracts  from  i* 
the  muriatic  acid.  This  mixture  is  sometimes  used  for 
filling  smelling-bottles. 

Experiment  d. —  Put  a  piece  of  tin,  the  size  of  a  pea, 

upon  a  bright  cent,  and 
hold  it,  by  means  of  a  pair 
of  forceps,  in  the  flame 
of  a  spirit-lamp ;  when  the 
tin  is  melted,  rub  it  upon 
the  cent  with  a  rag ;  it  will 
not  adhere  to  it.  Now  re- 
peat the  experiment,  but 

strew  at  the  same  time  some  powdered  sal  ammoniac 
upon  the  copper  surface  ;  the  tin  is  now  equally  diffused 
by  the  rubbing.  On  this  is  founded  the  important  ap- 
plication of  sal  ammoniac  in  tinning  and  soldering. 
The  muriatic  acid  of  the  ammonia  combines  with  the 
oxide  of  copper  formed  by  heating,  and  thereby  a  bright 
surface  of  copper  is  produced,  to  which  the  fused  tin 
will  firmly  adhere ;  hence  we  perceive,  also,  during  the 
process  of  tinning,  a  smell  of  free  ammonia.  Ammcma 
and  the  ammoniacal  salts  are  commonly  prepared  from 
sal  ammoniac. 

22* 


258 


ALKALIES 


Ammonia,  or  Water  of  Ammonia  (N  H3  -f-  Aq). 

230.  Experiment.  —  Pour  an  ounce  and  a  half  of 
water  upon  a  quarter  of  an  ounce  of  sal  ammoniac  and 
three  drams  of  slaked  lime,  contained  in  a  flask,  ar- 
ranged as  described  in  Fig.  106,  and  then  apply  a  mod- 
erate heat ;  the  lime  abstracts  from  the  sal  ammoniac 
as  has  already  been  seen,  its  muriatic  acid,  and  the  am- 
moniacal  gas  escapes.  As  soon  as  it  is  released  it  as- 
cends, since  it  is  nearly  one  half  lighter  than  common 
air ;  it  turns  red  litmus-paper  blue,  and  forms  thick 
white  fumes  of  sal  ammoniac  when  a  paper  moistened 
witli  muriatic  acid  is  held  in  it.  If  the  longer  limb  of 
the  tube  is  now  passed  nearly  to  the  bottom  of  a 
phial  containing  one  ounce  of  water,  the  gas  is  dis- 
solved, and  you  obtain  a  solution  of  ammonia  (water  of 
ammonia).  One  measure  of  water  can  absorb  move 
than  600  measures  of  ammoniacal  gas.  Since  much 
latent  heat  must  therefore  be  liberated,  the  receiving 
vessel  should  be  placed  in  cold  water.  A  second  tube, 
open  at  both  ends,  may  be  adapted  to  the  cork  01  the 
flask  to  prevent  the  water  being  forced  back  from  the 
phial  in  case  the  heat  should  accidentally  be  dimin- 
ished. The  tube  must  reach  to  the  bottom  of  the  flask, 
for  otherwise  the  gas  would  escape  through  it. 

The  solution  of  ammonia  is  lighter  than  water,  and 
so  much  the  lighter  in  proportion  to  the  amount  of  am- 
moniacal gas  it  contains ;  for  this  reason,  its  strength 
may  be  very  accurately  determined  by  its  specific 
gravity.  Its  most  important  properties  have  already 
been  mentioned.  On  account  of  its  corrosive  properties 
it  is  also  called  caustic  ammonia. 


AMMONIA. 


259 


231.  Hydrosulphuret  of  Ammonia,  or  Sulphuret  of  Am- 
monium (NH3,  HS). 

Experiment.  —  Pass  a  stream  of  sulphuretted  hydro- 
gen gas,  evolved  as  described  in  §  132,  into  a  solution  ot 
ammonia,  as  long  as  the  solution  continues  to  receive 
the  gas.*  TJiis  solution  must  be  kept  in  well-closed 
glass  bottles,  because  it  is  decomposed  on  exposure  to 
the  air,  and  becomes  yellow.  It  is  one  of  the  most 
important  chemical  reagents,  as  will  be  shown  here- 
after. 


Fig.  126. 


232.    Carbonate  of  Ammonia  (2  NH3,  3  C  O2  +  2  H  O). 

The  crude  carbonate  of  ammonia  has  al- 
ready been  treated  of;  the  pure  is  prepared 
from  sal  ammoniac  and  chalk,  by  sublima- 
tion. 

Experiment.  —  Introduce  a  mixture  of  half 
an  ounce  of  chalk  and  a  quarter  of  an  ounce 
of  sal  ammoniac  into  a  four-ounce  flask, 
having  a  thin  bottom;  place  it  in  a  sand- 
bath,  and  heat  it  over  a  spirit-lamp.  As 
soon  as  pungent  vapors  are  perceived,  invert 
a  somewhat  larger  flask  over  the  former, 
and  the  fumes  will  soon  condense  into  a 
white  saline  mass.  By  double  elective  affinity  there  are 
formed  volatile  carbonate  of  ammonia,  which  sublimes, 
and  chloride  of  calcium,  which  remains  behind,  since  it 
is  not  volatile. 

Carbonate  of  ammonia  (or,  more  correctly,  sesqui- 
carbonate  of  ammonia)  is  a  white  substance  having  a 
pungent  ammoniacai  odor,  which  gradually  attracts 
more  carbonic  acid  from  the  air,  and  becomes  bicarbo- 
nate of  ammonia.  This  salt  is  frequently  used  by 
bakers,  instead  of  yeast,  for  raising  gingerbread,  spice- 


260  ALKALIES. 

cakes,  &c.  (§  519) ;  it  escapes  in  the  heat  as  a  gas  from 
the  dough,  and  renders  it  light  and  porous. 

Other  ammoniacal  salts  may  easily  be  prepared  from 
the  carbonate  of  ammonia,  by  expelling  the  carbonic 
acid  by  means  of  a  stronger  one ;  for  instance,  by  sul- 
phuric, nitric,  or  acetic  acid,  &c. 

233.  Ammonia  from  putrefying'  Substances.  —  One 
other  source  of  ammonia  yet  remains  to  be  noticed.  It 
occurs  wherever  organic  substances  are  undergoing 
putrefaction  and  decay.  Carbonate  of  ammonia  is 
evolved  from  all  vegetable  and  animal  substances 
which  contain  nitrogen,  when  they  putrefy  or  decay  ; 
hence  the  pungent  odor  of  stables  and  manure-heaps 
If  you  put  a  bowl  containing  muriatic  acid  or  diluted 
sulphuric  acid  in  such  places,  the  odor  vanishes,  and  the 
muriatic  acid  is  gradually  converted  into  muriate  of 
ammonia,  and  the  sulphuric  acid  into  sulphate  of  am- 
monia. Thus  we  possess  in  the  acids  a  simple  and 
cheap  means  of  purifying  the  air  in  such  places.  Putrid 
urine  contains  so  much  carbonate  of  ammonia,  that  it 
is  used  instead  of  soap-water  for  washing  wool,  and 
indeed  even  for  the  preparation  of  muriate  of  ammonia 
itself. 

234.  When  we  reflect  upon  the  action  of  the  ani- 
mal substances  already  treated  of,  we  cannot  but  be 
surprised  to  find  how  very  much  the  nitrogen  contained 
in  them  varies  in  its  affinity  for  other  elements. 

The  nitrogen  of  organic  substances  combines,  — 

With  hydrogen,  at  common  temperatures,  forming 
ammonia  (decay). 

With  oxygen,  at  common  temperatures,  and  in  the 
presence  of  a  strong  base,  forming  nitric  acid  in  nitre 
beds. 

With  hydrogen,  on  the  application  of  heat  and  with- 
out access  of  air,  forning  ammonia  (dry  distillation). 


AMMONIA.  261 

With  carbon,  on  the  application  of  heat,  without  ac- 
cess of  air,  and  in  the  presence  of  a  strong  anhydrous 
base,  forming  cyanogen. 

With  hydrogen,  on  the  application  of  heat,  without 
access  of  air,  and  in  the  presence  of  a  hydrated  base, 
forming  ammonia. 

But  it  escapes  uncombined,  on  the  application  o( 
heat,  with  free  access  of  air  (complete  combustion). 

235.  The  Salts  of  Ammonia  afford  an  excellent  ma- 
nure for  soils.  They  are  the  principal  ingredients  in 
many  kinds  of  manure ;  and  therefore  we  should  en- 
deavour to  prevent  the  escape  of  ammonia  from  manure- 
heaps,  by  sprinkling  them  from  time  to  time  with  di- 
luted sulphuric  acid,  or  by  strewing  gypsum  over  them, 
whereby  sulphate  of  ammonia  is  formed,  which  does 
not  volatilize  at  common  temperatures.  When  bones 
decay,  carbonate  of  ammonia  is  likewise  produced  from 
the  gelatine,  and  to  this  is  to  be  ascribed  the  second 
beneficial  influence  which  pulverized  bones  exercise 
upon  the  growth  of  our  cultivated  plants  (§  176). 
Those  plants  which  grow  wild  can  receive  only  so 
much  ammonia  as  they  find  in  the  air ;  but  by  manur- 
ing we  give  a  much  larger  quantity  of  it  to  cultivated 
plants;  and  thus  is  in  part  explained  the  far  greater 
fertility  of  manured  arable  land  in  comparison  with 
that  which  is  not  manured. 

Ammonia  affords  another  example  of  the  circulation 
in  the  great  economy  of  nature,  similar  to  that  present- 
ed in  the  instances  of  carbonic  acid  and  water,  the  two 
other  principal  sources  of  nourishment  for  the  vegetable 
world ;  and  we  cannot  but  be  astonished  at  the  simple 
manner  in  which  the  Creator  has  connected  life  and 
death  with  each  other.  During  the  processes  of  putre- 
faction and  decay,  the  dead  animals  and  plants  are  coiv 


262 


ALKALIES. 


verted  into  carbonic  acid,  water,  and  ammonia;  and 
from  these  three  products  of  decay  are  reproduced  all  the 
innumerable  plants  which  cover  the  surface  of  our  earth. 

Fig.  127 


Dead  animals  and  planta.  Living  plants. 

236.  The  great  resemblance  of  ammonia  to  potassa 
and  soda  has  long  since  given  rise  to  the  conjecture,  that 
a  metal  might  also  be  concealed  in  it,  as  well  as  in  the 
potassa  and  soda.  If  a  body  —  for  instance,  cyanogen  — 
which  comported  itself  exactly  like  a  chemical  element, 
like  chlorine,  could  be  generated  from  nitrogen  and  car- 
bon, so  also  it  was  possible  that  a  body  might  be  formed 
from  nitrogen  and  hydrogen  wThich  should  comport  itself 
like  a  metal,  like  potassium.  Chemists  have  not  yet 
succeeded  in  separating  such  a  metal  from  ammonia  or 
its  salts;  nevertheless,  the  opinion  is  maintained  by 
many  of  them,  that  such  a  metal  does  really  exist,  and 
consists  of  one  atom  of  nitrogen  and  four  atoms  of  hy- 
drogen (NH4).  They  have  called  it  ammonium]  and, 
according  to  this  v?ew,  regard  hydrated  ammonia 
(NH3  -(-HO)  as  oxide  of  ammonium  (NH4  O),  mu- 
riate of  ammonia  (NH3  -f-  H  Cl),  as  chloride  of  ammo- 
nium (NH4  Cl),  &c.,  which  amounts  to  the  same  thing, 
since  the  constitution  of  these  two  bodies  is  not  changed, 
whether  the  hydrogen  is  considered  as  belonging  to  the 
water  or  to  the  muriatic  acid,  or  as  combined  with  the 
ammonia. 

A  compound  of  one  atom  of  nitrogen  and  two  atoms 
of  hydrogen  (NH2)  has  been  called  amide 


RETROSPECT    OF    THE    ALKALIES.  263 


LITHIUM. 

A  very  rare  base,  lithia  or  oxide  of  lithium,  occurs  in 
several  minerals  and  mineral  waters  ;  it  possesses  prop- 
erties analogous  to  those  of  potassa.  Many  salts  oi 
lithia  impart^a  beautiful  crimson  color  to  the  blow-pipe 
flame,  and  to'  the  flame  of  burning  alcohol. 


RETROSPECT  OF  THE  ALKALIES   (POTASSA,  SODA,  AND 
AMMONIA). 

1.  Of  all  bodies,  potassium  and   sodium  have  the 
greatest  affinity  for  oxygen ;  they  float  upon  water,  and 
decompose  it  with  great  violence. 

2.  Then*  oxides  are  the  most  powerful  bases.    The  ox- 
ide of  potassium  is  commonly  called  potassa,  or  caustic 
potassa ;  the  oxide  of  sodium,  soda,  or  caustic  soda  ;  and 
ammonia  may  also  be  regarded  as  caustic  ammonia. 

3.  These  three  oxides  are  commonly  called  alkalies^ 
^ilso   caustic    alkalies.      Formerly   potassa   was   called 
vegetable  alkali ;  soda,  mineral  alkali ;  and  ammonia, 
volatile  alkali. 

4.  The  alkalies  are  easily  soluble  in  water,  have  an 
alkaline  taste,   and  exert   a  strong  caustic   action   on 
animal  and  vegetable  substances. 

5.  The  alkalies  have  a  very  great  affinity  for  car- 
bonic acid.     They  absorb  it  eagerly  from  the  air,  and 
become  converted  into  alkaline  carbonates. 

6.  Carbonic  acid  cannot  be  expelled  from  the  alka- 
line carbonates  by  heating,  but  it  escapes  immediately, 
with  effervescence,  on  the  addition  of  other  acids. 

7.  The  alkaline  carbonates,  carbonate  of  potassa,  of 
soda,  and  of  ammonia,  are  easily  soluble  in  water,  and 
have  likewise  an  alkaline  taste  and  a  basic  reaction. 


264  ALKALINE    EARTHS. 

8.  Potassa  and  soda,  with  sand,  yield  melted  glass , 
and  with  fat,  a  soap,  which  is  soluble  in  water. 

9.  Most  of   the  salts  which  the  alkalies  form  with 
acids  are  soluble  in  water.     Most  of  the  potassa  salts 
are  permanent  in  the  air,  some  deliquescent ;  most  of 
the  soda  salts   contain   water  of   crystallization,   and 
effloresce  in  a  dry  atmosphere. 

10.  Potassa  and  soda  salts  are  not  volatile  in  the 
heat,  but  the  salts  of  ammonia  are  so. 

11.  A  weaker  base  will  often  remove  the  acid  from 
a  stronger  base,  when  it  forms  with  this  acid  an  insol- 
uble compound. 

SECOND  GROUP:     THE    ALKALINE    EARTHS. 

CALCIUM  (Ca). 
At.  Wt.  =  250.  —  Sp.  Gr.  ? 

Chalk,  or  Carbonate  of  Lime  (CaO,  CO2). 

237.  It  is  already  known  that  chalk  consists  of  car- 
bonate of  lime ;  it  was  used,  indeed,  in  several  of  the 
earlier  experiments  for  the  preparation  of  carbonic  acid. 
We  find  just  the  same  constituents  also  in  common 
limestone,  in  marble,  oyster-shells,  &c.  There  are 
whole  ridges  of  mountains  consisting  of  limestone,  and 
extensive  districts  having  a  lime  or  calcareous  soil ; 
Fi<*.  128  carbonate  of  lime  is  one  of  the  principal 

constituents  of  our  earth.     We  also  find 

Im W l/'i'M      ^  *n  fransPareirt  crystalline  forms,  rhom- 
jjL  :'jjjfr        bohedrons,  and  six-sided  prisms,  and  then 
call  it  calcareous  spar.     The  great  differ- 
ence which  these  stones  present  in  their  exterior  ap- 
pearance cannot  be  wondered  at,  for  we  see  a  similar 
variety  of  form  in  our  common  sugar ;  we  have  it  crys 


CALCIUM.  265 

tallized  in  candy,  granular-crystalline  in  loaf-sugar,  amor- 
phous in  bonbons,  and  pulverulent  in  pounded  sugar. 

All  limestones  effervesce  when  treated  with  an  acid, 
and  may  thus  generally  be  distinguished  from  other 
stones.  If  you  smear  a  piece  of  limestone  in  single 
spots  with  fat  or  some  varnish-paint,  and  then  pour 
upon  it  an  acid  (a  weak  solution  of  nitric  acid  is  the 
best),  the  lime  dissolves  in  those  places  only  which  are 
unprotected  by  the  fat  or  paint,  the  greasy  spots  ac- 
cordingly remaining  raised.  If  a  stone  thus  prepared  is 
passed  over  with  printing-ink,  this  will  adhere  only  to 
the  elevated  places,  and  may  be  transferred  from  them 
to  paper.  This  is  the  method  used  for  engraving  on 
stone,  and  the  limestones  used  in  this  kind  of  engrav- 
ing are  called  lithographic  stones. 

Experiment. —  Blow  air  into  lime-water,  through  a 
glass  tube;  a  precipitate  of  carbonate  of  lime  is  formed 
(see  Fig.  81) ;  continue  the  blowing,  and  the  precipi- 
tate will,  for  the  most  part,  dissolve  again.  The  car- 
bonic acid  first  precipitates  the  lime,  then  it  dissolves 
it  again.  Carbonate  ,of  lime  is  quite  insoluble  in 
water,  bat  is  soluble  in  water  impregnated  with  car- 
bonic acid.  Let  half  of  the  liquid  remain  exposed  to 
the  air,  it  will  gradually  become  turbid,  and  carbonate 
of  lime  will  be*  deposited ;  boil  the  other  half  in  a  test- 
tube,  bubbles  of  carbonic  acid  will  escape,  and  carbo- 
nate of  lime  will  be  rapidly  precipitated.  What  here 
happens  cm  a  small  scale  frequently  occurs  in  nature 
on  a  large  scale.  The  water,  as  it  trickles  through  the 
earth  in  those  places  where  the  decay  of  organic  mat- 
ter is  going  on,  finds  carbonic  acid  ;  therefore  almost  all 
spring-water  contains  carbonic  acid.  The  carbonic  acid 
water  so  formed  finds  in  almost  all  earths  and  stones 
carbonate  of  lime,  some  of  which  it  dissolves ;  therefore 
23 


266  ALKALINE    EARTHS. 

almost  all  spring-water  contains  carbonate  of  lime  (hard 
water).  When  this  water  flows  along  in  brooks,  the  car- 
bonic acid  escapes  again,  and  the  carbonate  of  lime  is 
deposited  as  sediment ;  this  water,  free  from  lime,  is  now 
called  soft  water.  The  same  thing  happens  when  water 
containing  lime,  as  it  percolates  through  the  earth  or  fis- 
sures in  rocks,  meets  with  hollows  and  caverns ;  here  the 
carbonate  of  lime  frequently  deposits  itself  in  solid  mass- 
es, called  stalactites.  The  walls  of  cellars  and  bridges 
are  sometimes  found  covered  with  an  incrustation  of  sta- 
lactites. The  calcareous  tufa  deposited  from  the  Carls- 
bad waters  also  consists  principally  of  carbonate  of 
lime.  If  you  boil  hard  water,  carbonate  of  lime  is  also 
precipitated ;  this  happens  especially  when  large  quan- 
tities of  it  are  evaporated,  as  in  steam-boilers.  Peas 
and  beans,  boiled  in  hard  water,  become  incrusted  with 
a  thin  coating  of  lime,  which  prevents  the  water  from 
penetrating,  so  that  they  do  not  become  soft ;  for  such 
purposes,  the  water  should  previously  be  boiled,  or  ex- 
posed for  some  time  to  the  air. 

Caustic  Lime,  or  Quicklime  (Oxide  of  Calcium,  CaO). 

238.  Experiment. —  Put  a  piece  of  chalk  upon  coal, 
and  heat  it  strongly  before  ths  blow-pipe  for  several 
minutes ;  it  will  then  become  much  lighter  than  before, 
lose  its  marking  properties,  and  will  no  longer  effervesce 
with  acids ;  it  has  by  the  heating  lost  its  carbonic  acid, 
and  is  now  called  burnt  lime.  If  a  portion  of  it  is 
placed  on  moistened  red  litmus-paper,  it  causes  blue 
spots ;  consequently  it  has  a  basic  reaction,  which  chalk 
has  not. 

For  burning  large  masses  of  chalk  or  limestone,  kilns 
of  the  annexed  form  are  constructed,  a  is  the  fire-door, 
with  the  grate,  upon  which  pit-coal  or  turf  is  burnt;  b,  the 


CALOIUM. 


267 


Fig.  129. 


opening  lor  the  draught  of  air ; 
c  and  d,  the  ash-pit.  In  this,  as 
in  the  flame-furnace,  the  flame 
only  enters  the  kiln,  which  is 
filled  with  limestone ;  conse 
quently  the  lime  cannot  be 
rendered  impure  by  the  ashes 
of  the  fuel.  A  kiln  is  usually 
provided  with  several  such 
furnaces,  e  and  /are  the  dis- 
charge outlets  for  extracting 
the  lime,  when  it  is  well  cal- 
cined, fresh  carbonate  of  lime  being  introduced  at  the 
top  as  the  burnt  lime  is  removed.  Such  furnaces  may 
be  kept  going  for  years  without  interruption. 

Quicklime  has  two  strong  affinities,  namely,  for  wa- 
ter and  for  carbonic  acid.  On  exposure  to  the  air  it 
first  attracts  water,  and  thereby  crumbles  into  powder, 
—  it  is  slaked;  afterwards  it  absorbs  also  carbonic 
acid,  when  it  again  effervesces  with  acids.  The  rapid 
slaking  of  lime  by  drenching  with  water,  and  the  con- 
sequent evolution  of  heat,  have  been  previously  treated 
of  (§  33).  Three  pounds  of  lime  combine  with  one 
pound  of  water,  forming  a  fine  powder  of  hydrate  of 
tirr,3  (CaO-f-HO),  or  slaked  lime.  When  mixed 
with  water  into  a  paste,  it  is  mortar ;  if  more  water  is 
added,  it  becomes  milk  of  lime;  and  when  mixed  with 
600  times  its  quantity  of  water,  a  clear  solution,  lime- 
water,  is  obtained.  Like  Glauber  salts,  it  is  much 
more  soluble  in  cold  than  in  hot  water,  the  latter  dis- 
solving only  half  as  much  as  the  former.  On  account 
of  the  great  affinity  of  burnt  lime  for  water,  it  may  be 
employed  for  drying  damp  places,  and  for  preparing  an- 
hydrous or  absolute  alcohol  from  the  common  alcohol 


268 


ALKALINE    EARTHS. 


Examples  of  the  avidity  with  which  quicklime  com 
bines  with  carbonic  acid  have  already  been  given, 
under  combustion,  and  in  the  preparation  of  caustic 
potassa  and  of  caustic  soda.  Hence  it  is  very  useful 
for  purifying  air  which  contains  much  carbonic  acid; 
for  instance,  the  air  in  old  cellars,  wells,  mines,  or  in  cel- 
lars in  which  fermenting  Liquors,  as  must,  wort,  brandy 
mash,  &c.,  are  kept.  Milk  of  lime  is  also  commonly 
used  for  abstracting  from  crude  illuminating  gas  its 
carbonic  acid,  as  well  as  the  admixture  of  sulphuretted 
hydrogen.  It  is  likewise  in  general  use  for  white- 
washing ;  it  becomes  quickly  white  and  dry,  and  then 
it  is  no  longer  hydrate  of  lirne,  but  chalk. 

239.  Lime  as  Mortar.  —  Glue  is  used  for  joining  to- 
gether pieces  of  wood ;  and  mortar,  a  mixture  of  lime 
and  sand,  for  cementing  together  stones.  This  is  the 
most  important  application  of  lime.  A  mixture  of  lime 
and  sand,  on  exposure  to  the  air,  gradually  forms  into 
a  hard  and  stony  mass.  This  consolidation  is  to  be  as- 
cribed to  three  causes ;  —  1st,  the  water  evaporates,  and 
the  hydrate  of  lime  remains  behind  as  a  cohesive  mass ; 
2d,  the  lime  attracts  carbonic  acid  from  the  air,  and  there 
is  formed  a  mixture  of  hydrate  of  lime  and  carbonate 
of  lime,  which  possesses  greater  firmness  than  either 
body  separately;  3d,  on  the  surface  of  the  sand  a 
chemical  combination  is  gradually  formed  of  the  silicic 
acid  with  the  lime,  both  becoming,  as  it  were,  incorpo- 
rated together.  This  explains  the  remarkable  hardness 
of  the  mortar  in  old  buildings.  When  our  structures 
of  the  present  day  shall  have  stood  for  centuries,  the 
mortar  about  them  will  certainly  possess  the  same  de- 
gree of  firmness,  provided  good  quartz  sand  has  been 
employed  in  its  preparation,  and  not  the  argillaceous 
san  1  so  often  used.  Sand  also  diminishes  the  shrink 


CALCIUM. 

ing  or  contraction  of  the  mortar,  and  prevents  its  crack 
ing  as  it  becomes  dry.     Old  mortar   accordingly  con- 
sists of  hydrate  of  lime,  carbonate  of  lime,  silicate  of 
lime,  and  silica  (sand). 

If  you  burn  a  limestone  in  which  clay  is  contained, 
or  an  intimate  mixture  of  chalk  with  one  fifth  of  clay, 
you  will  obtain  a  burnt  lime,  which,  when  mixed  with 
water  and  sand,  yields  a  mortar  that  hardens  quickly, 
like  plaster  of  Paris,  and  becomes  as  hard  as  stone  un- 
der water ;  it  is  called  hydraulic  cement,  and  is  well 
adapted  for  building  piers  of  bridges,  or  other  structures 
under  water.  Clay  is  silicate  of  alumina;  therefore 
hydraulic  cement  is  an  intimate  mixture  of  quicklime 
with  silicate  of  alumina. 

240.  Further  Experiments  with  Lime. 

Experiment.  —  Wrap  a  piece  of  quicklime  in  paper 
or  in  a  linen  rag,  and  set  it  aside  for  some  weeks  ;  the 
paper  and  the  linen  will  become,  after  a  time,  so  rotten 
as  to  be  easily  torn  ;  the  lime,  to  use  a  common  ex- 
pression, has  eaten  them.  Thus  quicklime,  like  potassa 
or  soda,  exerts  a  corrosive  action  upon  organic  sub- 
staiir:e«,  and  for  this  reason  it  is  also  frequently  called 
caustic  lime.  If  you  rub  between  the  fingers  lime 
made  into  a  paste  with  water,  you  readily  perceive 
by  the  feeling  its  caustic  action  upon  the  skin.  In 
tanneries  the  hides  are  immersed  in  milk  of  lime,  in 
order  to  loosen  them,  so  that  the  hair  may  easily  be 
rubbed  off;  and  in  agriculture,  lime  is  mixed  with 
weeds,  such  as  couch-grass,  &c.,  to  accelerate  their  de- 
composition. It  is,  however,  altogether  wrong  to  mix 
lime  with  manure  that  is  already  in  a  state  of  decay 
and  putrefaction,  because  it  contains  ammoniacal  salts, 
the  ammonia  of  which  would  be  set  free  bv  the  lime 
23* 


270 


ALKALINE     EARTHS. 


and  escape ;  the  manure  would  thus  lose  much  of  its 
efficacy. 

Many  plants,  as  peas,  clover,  tobacco,  flourish  only  in 
a  soil  containing  lime.  If  you  burn  such  plants,  you 
always  obtain,  let  them  grow  wherever  they  will,  ashes 
which  contain  more  than  half  their  weight  of  lime  salts ; 
we  call  such  plants  lime  plants^  and  must  conclude  from 
these  two  facts,  that  lime  is  as  indispensable  for  the  life 
of  many  plants,  as  common  salt  is  for  that  of  animals. 
Thus  agriculturalists  possess  in  lime  an  excellent  ma- 
nure for  those  fields  where  lime  is  deficient. 

Experiment.  —  Dissolve  a  little  soap  in  hot  water,  and 
add  lime-water  to  it ;  the  solution  becomes  turbid,  and 
afterwards  white  flakes  are  deposited,  which  feel  sticky 
when  rubbed  between  the  fingers.  The  same  thing  is 
observed  on  washing  with  soap  and  lime-water ;  the 
soap  neither  lathers  nor  cleanses.  Therefore,  water 
containing  lime,  the  so-called  hard  water,  cannot  be 
used  for  washing.  The  viscous  mass  which  separates 
is  lime  soap,  a  combination  of  the  fatty  substances  con- 
tained in  the  soap  with  lime.  Potassa  and  soda  soap 
are  soluble  in  water,  lime  soap  is  insoluble. 

Caustic  lime  is  a  combination  of  oxygen  with  a 
metal,  which  has  received  the  name  calcium  (Ca)  ;  it 
may  therefore  be  called,  also,  oxide  of  calcium  (Ca  O). 
Lime  is,  next  to  the  alkalies,  one  of  the  .strongest  bases. 

Gypsum,  or  Sulphate  of  Lime  (Ca  O,  S  O3  -f  2  H  O). 

241.  Experiment.  —  Expose  to  a  moderate  heat  in  an 
iron  vessel  the  gypsum  obtained  in  former  experiments 
(§§  164,  1T6),  stirring  it  during  the  heating,  which  must 
be  continued  till  vapors  cease  to  escape  from  it;  it  will 
afterwards  weigh  one  fifth  less  than  before,  and  is  called 
calcined  gypsum.  The  loss  of  weight  is  owing  to  the 


CALCIUM.  271 

water  of  crystallization  which  was  driven  off  by  the  heat. 
A  temperature  of  120°  C.  is  sufficient  to  effect  this. 
Experiment.  —  Wind  round  the  brim  of  a  dollar-piece 
Fja.  130  a  strip  of  paper,  firmly  securing  the 

loose  end  of  it  by  sealing-wax.  A 
box  is  thus  made,  the  bottom  of 
which  is  formed  by  the  dollar.  Now 
mix  two  even  spoonfuls  of  calcined 
gypsum  and  a  spoonful  of  water  into 
a  paste,  stir  it  round  quickly,  and  pour  the  paste  into 
the  box ;  after  a  few  minutes  it  will  become  so  hard, 
that  both  the  paper  and  the  coin  can  be  removed.  A 
reversed  impression  of  the  coin  will  appear  on  the  un- 
der side  of  the  gypsum.  After  this  is  perfectly  dry, 
smear  the  impression  with  a  strong  solution  of  soap, 
mixed  with  a  few  drops  of  oil,  and  upon  pouring  over  it 
some  of  the  gypsum  paste,  a  true  stamp  of  the  coin  will 
be  obtained.  The  rapid  hardening  may  be  thus  ex- 
plained; the  anhydrous  burnt  gypsum  again  chemically 
combines  with  as  much  water  as  it  has  lost  during  the 
ignition.  If  the  gypsum  had  been  heated  above  160°  C., 
it  would  not  have  hardened ;  it  having  then  lost  its  affin- 
ity for  water.  In  a  similar  manner,  figures  of  plaster  of 
Paris  are  made  in  hollow  moulds.  Gypsum  is  used  in 
architecture  for  making  on  walls  and  ceilings  various 
ornamental  figures  and  designs,  called  stucco-work. 

Gypsum  is  a  mineral  of  very  frequent  occurrence  in 
nature,  and  in  some  localities,  as  at  Jena,  it  forms  entire 
ranges  of  hills.  When  crystallized  in  tables  it  is  termed 
selenite,  and  the  white,  compact,  granular  variety  is 
called  alabaster.  It  is  also  frequently  contained  in 
spring-water. 

Gypsum  is  very  sparingly  soluble  in  water,  half  an 
ounce  of  the  latter  dissolving  only  half  a  grain  of 
gypsum. 


272  ALKALINE    EARTHS. 

To  detect  gypsum  in  a  liquid,  add  to  one  portion 
a  solution  of  chloride  of  barium,  whereby  the  presence 
of  sulphuric  acid  is  indicated ;  and  to  another  portion, 
a  solution  of  oxalic  acid,  by  which  the  presence  of 
lime  is  shown.  Oxalic  acid  is  the  most  certain  test  for 
lime  salts  (§  197). 

That  gypsum,  as  well  as  quicklime,  is  a  valuable 
manure  for  many  plants,  especially  for  the  leguminous 
plants,  is  well  known  to  farmers,  who  frequently  spread 
it  over  their  barley  and  clover  fields.  The  plants  here- 
by not  only  absorb  the  lime,  but  also  the  sulphur  of  the 
sulphuric  acid.  Gypsum  has  also  a  beneficial  effect  on 
the  growth  of  plants,  as  it  absorbs  the  carbonate  of  am- 
monia contained  in  the  air  and  in  rain-water,  and  fixes 
it  in  the  soil,  these  two  salts  being  converted  respective- 
ly into  sulphate  of  ammonia  and  carbonate  of  lime. 

When  gypsum  is  heated  to  redness  with  charcoal, 
sulpliaret  of  calcium  is  obtained,  which,  like  the  liver  of 
sulphur,  evolves  sulphuretted  hydrogen,  when  drenched 
with  diluted  acid. 

242.  Phosphate  of  lime  constitutes,  as  already  men- 
tioned, the  principal  ingredient  of  bones;  it  occurs  in 
the  mineral  kingdom  as  apatite  and  phosphorite. 

243.  Nitrate  of  lime  (Ca  O,  N  O5)  is  always  formed 
when  azotized  substances  and  lime  remain  for  some 
time  together  in  contact  (§  207).      This  salt  is  very 
often  generated  in  the  plaster  of  walls,  in  those  build- 
ings where  urinous  liquids  or  ammoniacal  fumes  are 
present,  as  in  stables.     The  lime  loses  hereby  its  adhe- 
siveness, and  crumbles,  especially  when  the  rain  washes 
out  the  easily  soluble  nitrate  of  lime.     This  process  ia 
commonly  called  the  crumbling  away  of  the  walls.* 

*  "  The  injury  thus  done  to  a  building  by  the  formation  of  soluble  ni- 
trates has  received  (in  Germany)  a  special  name,  Saltpetrefrass  (produc 
tion  of  soluble  nitrate  of  lime)."  —  Liebig's  Ag.  Chem. 


CALCIUM.  273 

CJiloride  of  Lime,  or  Hypochlorite  of  Lime  (Ca  O,  Cl  C 

+  Ca  Cl). 

244.  Experiment.  —  Mix  half  an  ounce  of  slaked  lime 
with  six  ounces  of  water,  and  conduct  into  this  milk  of 
lime,  with  frequent  agitation,  as  much  chlorine  as  will 
evolve  from  two  ounces  of  muriatic  acid  and  half  an 
ounce  of  black  oxide  of  manganese.  The  liquid,  clari- 
fied by  standing,  may  be  regarded  as  a  solution  of 
chloride  of  lime,  and  must  be  kept  protected  from  the 
air  and  light.  It  would  seem  at  first  as  if  the  chlorine 
united  directly  with  the  lime,  but  this  is  not  possible, 
since,  as  a  general  rule,  simple  bodies  cannot  combine 
with  compound  bodies.  The  process  is  as  follows. 
Half  of  the  lime  releases  its  oxygen,  and  is  converted 
into  calcium,  which,  being  a  simple  body,  combines 
with  chlorine ;  the  oxygen,  liberated  from  the  lime,  com- 
bines with  the  rest  of  the  chlorine,  forming  hypochlo- 

rous  acid  (Cl  O),  which, 
Bleaches,  being  a  compound  body, 

can  now  unite  with  the 

other   half  of   the   lime. 

Thus  are  formed  a  haloid 
DbTcLnhnt  salt>  chloride  of  calcium, 

and  an  oxygen  salt,  hij- 
pochlorite  of  lime.  The  latter  is  the  essential  agent, 
the  bleaching  power,  in  the  chloride  of  lime ;  chloride 
of  calcium  is  to  be  regarded  only  as  an  unnecessary 
make-weight.  Accordingly  the  name  of  chloride  of 
lime  is  incorrect,  but,  like  many  other  terms  of  general 
acceptation,  it  would  be  inconvenient  not  to  retain  it 
It  must  not  be  forgotten,  however,  that  chloride  of  lime 
is  a  very  different  body  from  chloride  of  calcium. 

By  the  old  process,  bleaching  required  weeks,  and 
even  months  ;  now,  by  moans  of  phlorido  of  lime,  cotton 


274  ALKALINE    EARTHS 

and  linen  are  bleached  in  as  many  days.  For  this  rea- 
son, vast  quantities  of  chloride  of  lime  are  manufactured 
in  chemical  laboratories,  and  are  consumed  in  bleach  er- 
ies  and  calico  print-works.  The  preparation  of  it  on  a 
large  scale  is  conducted  upon  the  same  principle  as 
that  just  described,  except  that,  instead  of  milk  of 
lime,  slaked  lime  is  used,  which  is  spread  upon  hurdles 
in  chambers,  and  which,  like  milk  of  lime,  absorbs  the 
chlorine.  Chloride  of  lime,  thus  prepared,  is  a  gran- 
ular powder,  which  absorbs  moisture  from  the  air,  and 
emits  the  odor  of  chlorine.  Upon  adding  water  to  it, 
the  same  liquid  is  obtained  as  that  prepared  above. 

245.  Experiments  with  Chlorine. 

Experiment  a.  —  Immerse  a  piece  of  cotton,  printed 
with  various  colors,  into  a  solution  of  chloride  of  lime ; 
if  there  are  vegetable  colors  among  those  with  which 
the  cotton  is  printed,  they  will  bleach,  though  but 
slowly. 

Experiment  b.  —  Proceed  in  the  same  manner,  add- 
ing, however,  to  the  solution  some  drops  of  diluted 
muriatic  or  sulphuric  acid ;  the  bleaching  will  then  take 
place  instantaneously,  attended  with  the  evolution  of  a 
strong  smell  of  chlorine.  The  acids  expel  the  feeble, 
hypochlorous  acid,  and  this  is  resolved  into  oxygen  and 
chlorine.  If  you  let  the  material  remain  for  some  time 
in  the  solution  of  the  chloride  of  lime,  the  vegetable 
fibres  will  also  be  decomposed  (eaten)  by  the  chlo- 
rine, and  will  lose  their  firmness. 

Experiment  c.  —  Drop  some  tincture  of  indigo  into  a 
portion  of  the  solution ;  the  indigo  is  immediately  de- 
composed, and  its  blue  color  changed  to  yellow.  Con- 
tinue to -add  the  indigo  till  the  blue  color  remains  un- 
affected, and  note  the  quantity  of  indigo  used ;  in  this 


CALCIUM. 

manner  the  strength  of  the  different  sorts  of  c  hloride  of 
lime  may  be  determined,  for  the  more  hypochlorous 
acid  there  is  contained  in  the  chloride  of  lime,  so  much 
the  more  indigo  it  is  able  to  deprive  of  its  color. 

Experiment  d.  —  Chloride  of  lime,  as  well  as  free 
chlorine,*  destroys  the  noxious  effluvia  evolved  during  rhe 
decay  or  putrefaction  of  organic  substances.  The  im- 
pure air  of  stables  is  destroyed  by  strewing  about  chlo- 
ride of  lime,  and  damp  cellars  are  purified  by  washing 
the  floors  and  walls  with  a  solution  of  it,  &c. 

In  all  these  decompositions,  the  chlorine  always 
combines  with  the  hydrogen  of  the  coloring  and  odor- 
ous matter. 

If  chlorine  is  conducted  into  a  solution  of  carbonate 
of  soda,  instead  of  into  milk  of  lime,  we  obtain  hypo- 
chlorite  of  soda,  likewise  a  bleaching  liquid,  known  as 
Labarraque*  s  disinfecting  liquor. 

Chloride  of  Calcium,   or  Muriate  of  Lime    (Ca  Cl,  or 
CaO,HCl). 

246.  Experiment.  —  Mix  muriatic  acid  with  half  its 
quantity  of  water,  and  add  to  it  pieces  of  chalk  until 
effervescence  ceases  ;  then  evaporate  the  filtered  solution 
to  the  consistency  of  a  syrup.  We  obtain  from  this, 
on  cooling,  large  prismatic  crystals  of  chloride  of  calci- 
um, which  must  be  quickly  dried  by  pressure  between 
folds  of  blotting-paper,  and  kept  carefully  excluded  from 
the  air,  as  they  are  exceedingly  deliquescent.  Tn  the 
winter  season,  this  salt  may  be  employed  for  freezing 
mercury.  For  this  purpose  let  it  remain  one  night  in  a 
cold  place,  then  grind  it  up  in  a  cold  mortar,  and  mix  it 
with  snow ;  if  some  mercury,  contained  in  a  glass  tube, 
is  now  introduced  into  the  mixture,  it  will  become 
solid,  and  a  spirit-of-wine  thermometer  will  indicate  a 


276  ALKALINE    EARTHS. 

temperature  of  — 40°  C.      The    snow   and   the   chlo 
ride  of  calcium   melt;   from  two  solid  bodies  is  thus 
formed   a   liquid,   and  during  this  transition   a   great 
quantity  of  free  heat  must  necessarily  become  latent. 

Crystals  of  chloride  of  calcium  contain  half  their 
weight  of  water  of  crystallization  ;  on  being  heated,  the 
water  passes  off,  and  we  obtain  fused  chloride  of  calcium, 
one  of  the  most  hygroscopic  salts,  which  may  be  em- 
ployed for  preparing  absolute  from  common  alcohol,  and 
for  drying  certain  gases.  For  this  latter  purpose,  fill  a 

capacious    glass 

Fig.  131.  ° 

tube   with   frag- 
ments of  it,  and 

A  adapt     to     each 

end  of  the  tube; 

by  means  of  perforated  corks,  two  small  glass  tubes, 
through  which  the  gas  may  be  transmitted ;  during  its 
passage,  all  the  moisture  will  be  abstracted  from  it  by 
the  chloride  of  calcium.  In  the  preparation  of  ammo- 
nia (§  230),  chloride  of  calcium  is  obtained  as  a  secon- 
dary product.  It  has  already  been  mentioned  (§  244), 
that  it  forms  a  constituent  (though  a  useless  one)  of 
chloride  of  lime. 

247.  Fluoride  of  Calcium  (Ca  Fl),  commonly  called 
fluor-spar,  is  a  mineral  of  frequent  occurrence  in  nature, 
and  is  often  found  in  cubic  crystals  of  great  beauty. 
It  is  easily  fused  by  heat  (hence  its  name),  and  it  yields 
when  treated  with  sulphuric  acid,  hydrofluoric  acid 
(§190). 


BARIUM  AND  STRONTIUM.  277 

BARIUM  AND  STRONTIUM  (Ba  and  Sr). 
At.  Wt.  =  855.  — At.  Wt.  =  548. 

248.  These  two  metals  have  so  great  a  similarity  to 
calciura  in  their  properties  and  combinations,  that  they 
may  be  regarded  as  brethren.  Their  oxides  are  termed 
baryta  (Ba  O)  and  strontia  (Sr  O),  and  when  water  is 
added  to  them  they  evolve  heat,  as  is  the  case  with 
lime,  and  afford  a  basic  reaction.  The  carbonates  of 
baryta  and  strontia  are,  like  chalk,  insoluble  in  water, 
and  at  a  strong  heat  lose  their  carbonic  acid,  yet  not 
so  readily  as  chalk.  The  salts  of  lime,  as  has  been 
seen,  are  very  easily  prepared  by  merely  adding  acids 
to  marble  or  chalk  ;  but  the  salts  of  baryta  and  strontia 
are  not  so  easily  obtained,  because  baryta  and  strontia 
are  rarely  found  in  nature  combined  with  carbonic, 
but  most  frequently  with  sulphuric  acid ;  consequently, 
with  an  acid  which  is  stronger  than  all  others.  It 
is  therefore  necessary,  as  in  the  preparation  of  soda, 
to  adopt  a  circuitous  method ;  it  must  first  be  reduced 
to  a  sulphuret  by  heating  with  charcoal ;  this  sulphuret 
may  be  afterwards  decomposed  by  acids. 

Chloride  of  barium,  or  muriate  of  baryta  (Ba  Cl),  is 
the  most  common  soluble  salt  of  baryta.  It  crystallizes 
ill  transparent  tables,  and  is  used  in  medicine.  The 
chemist  also  makes  use  of  it  as  the  surest  test  for  sul- 
phuric acid  and  the  sulphates  (§  171).  Nitrate  of 
baryta  serves  also  for  the  same  purpose. 

Sulphate  of  Baryta  (BaO,  SO3). 

Experiment.  —  Dissolve  some  Glauber  salts  in  water, 
and  add  a  solution  of  chloride  of  barium,  as  long  as 
any  precipitate  is  produced ;   chloride   of  sodium  and 
24 


278 


ALKALINE    EARTHS. 


soluble, 


insoluble, 


sulphate  of  baryta  are 
formed  by  double  elec- 
tive affinity  ;  the  latter  is 
quite  insoluble  in  water, 
and  also  in  acids,  and  is 
therefore  thrown  down  as  a  heavy  white  powder.  The 
ponderous  mineral,  known  as  heavy  spar,  which  is 
frequently  found  in  beautiful  tabular  crystals,  associat- 
ed particularly  with  metallic  ores,  is  the  native  sul- 
phate of  baryta.  Baryta  and  the  baryta  salts  are  pre- 
pared from  it.  This  mineral,  when  ground  to  powder, 
is  frequently  used  for  the  adulteration  of  white  lead. 

The  most  remarkable  characteristic  of  the  strontia 
salts  is  that  of  communicating  a  crimson  tint  to  the 
flame  of  burning  substances.  Nitrate  of  strontia,  like 
the  other  nitiates,  deflagrates  upon  burning  charcoal, 
and  is  used  for  producing  a  crimson  flame  in  fireworks, 
prepared  from  potassa,  sulphur,  and  charcoal.  Chloride 
of  strontium,  or  muriate  of  strontia,  is  soluble  in  alcohol, 
and  imparts  to  its  flame  a  crimson  color. 

MAGNESIUM  (Mg). 
At.  Wt.  =  158.—  Sp.  Gr.  =  1.7. 

Epsom  Salt,  or  Sulphate  of  Magnesia 
(MgO,  SO3  +  7HO). 

249.  Envelop  in  a  fold  of  strong  paper  a  fragment 
of  serpentine  mineral  ;  crush  it  with  a  hammer,  then 
pulverize  it  in  an  iron  mortar,  and  mix  half  an  ounce 
of  it  in  a  porcelain  basin  with  some  common  sulphuric 
acid  to  the  consistency  of  a  paste,  and  set  it  aside  for 
some  days  in  a  warm  place.  Then  stir  in  carefully  an 
ounce  and  a  half  of  water,  let  the  mixture  stand  again 
for  some  days,  and  finally  decant  the  warm  clear  liquid. 


MAGNESIUM.  279 

It  >fill  have  a  green  tint,  owing  to  the  presence  of  some 
protoxide  of  iron.  When  boiling,  add  gradually  nitric 
acid  to  it,  until  the  liquid  has  assumed  a  yellow  color : 
the  protoxide  will  be  thereby  converted  into  sesqu: 
oxide  of  iron.  If  evaporated  until  a  pellicle  is  formed, 
crystals,  will  be  deposited,  which  must  be  dissolved 
again  in  boiling  water,  and  recrystallized.  Sulphate  of 
sesquioxide  of  iron,  which  can  be  crystallized  only  with 
difficulty,  will  remain  in  the  mother  liquor.  The  crys- 
tals have  a  bitter  taste.  Their  constituents  are  sul- 
phuric acid  and  a  base,  called  magnesia  (Mg  O).  The 
taste  of  all  the  soluble  salts  of  magnesia  is  bitter.  This 
base  is  combined  in  the  serpentine  with*  silicic  acid, 
which  the  stronger  sulphuric  acid  displaces  and  com- 
bines with,  forming  a  soluble  salt,  while  the  silica  re- 
mains behind  undissolved.  We  find  silicate  of  magne- 
sia also  in  other  minerals;  for  instance,  in  meerschaum, 
soap-stone,  talc,  asbestos,  hornblende,  and  in  several 
varieties  resembling  mica,  &c.  All  these  minerals 
have  a  slippery  or  greasy  feeling,  and  are  mostly  in- 
cluded under  the  general  head  of  talc.  Magnesia  is 
sometimes  called  also  talc  earth. 

Epsom  salt  is  one  of  the  most  common  purgatives, 
and  is  much  employed  in  medicine.  We  usually  ob- 
tain it  in  commerce,  not  in  perfect  crystals,  but  in  the 
f  3rm  of  small  acicular  crystals,  owing  to  the  evaporation 
having  been  carried  on  after  the  formation  of  the  pel- 
licle, and  to  the  stirring  of  the  mass  while  cooling. 
Consequently  a  disturbed  crystallization  has  taken 
place.  In  many  places,  for  instance,  at  Saidschutz  in 
Bohemia,  there  are  springs  holding  Epsom  salt  in  so- 
lution, and  they  are  often  resorted  to  by  invalids.  If 
their  waters  are  evaporated,  this  salt  is  likewise  ob 
tained  from  them. 


ALKALINE    EARTHS. 


Carbonate  of  Magnesia. 

250.  Experiment. — Dissolve  half  an  ounce  of  Ep- 

som salt  in  four  ounces  of  cold 
water,  and  add  a  solution  of 
carbonate  of  soda  as  long  as  a 
precipitate  continues  to  fall. 
The  precipitate  is  carbonate  of 
magnesia,  but  sulphate  of  soda 
remains  in  the  solution ;  thus 
the  Epsom  salt  and  carbonate 
of  soda  have  exchanged  their 
acids.  The  milky  liquid  is  now 
heated  to  boiling,  filtered,  and 
the  precipitate  washed  and 
dried  ;  it  is  very  light  and  white, 

and  is  known  as  the  magnesia  alba  of  the  apothecaries' 
shops.  During  the  ebullition,  some  carbonic  acid 
escapes.  Carbonate  of  magnesia  is  also  found  in  many 
kinds  of  marble  and  limestone,  called  dolomite. 

Magnesia  (Oxide  of  Magnesium)  (MgO). 

If  you  heat  carbonate  of  magnesia  to  redness,  it 
loses,  like  chalk,  its  carbonic  acid,  and  at  the  same  time 
the  water  with  which  it  was  chemically  combined  ;  the 
magnesia  remains  behind  as  a  light  powder,  commonly 
called  calcined  magnesia  (oxide  of  magnesium).  It  is 
nearly  insoluble  in  water,  and  consists  of  a  metal,  mag- 
nesium^ and  of  oxygen. 

CJiloride  of  Magnesium,  or  Muriate  of  Magnesia 
(MgCl,  or  MgO,  HC1). 

251.  Experiment. —  Add  to  carbonate  of   magnesia 
some  diluted  muriatic  acid ;  the  carbonic  acid  escapes 


RETROSPECT.  281 

but  the  chloride  of  magnesium  is  dissolved  in  the 
liquid.  This  salt  is  always  found  associated  with  com- 
mon salt,  and  as  it  is  very  soluble  and  hygroscopic,  it 
remains  in  the  mother  liquor  on  the  evaporation  ol 
salt-springs.  Therefore  Epsom  salt  may  also  be  ob- 
tained from  fcjie  mother  liquor,  by  converting  chloride 
of  magnesium  into  sulphate  of  magnesia.  The  bitter 
taste  of  sea- water  is  owing  to  this  salt. 

Experiment.  —  Put  into  a  glass  of  water  a  few  drops 
of  the  above  solution,  or  a  little  Epsom  salt,  and  then 
add  to  it  a  solution  of  phosphate  of  soda  ana  some 
ammonia ;  the  liquid  first  becomes  turbid,  and  finally  a 
crystalline  precipitate  is  deposited  (phosphate  of  mag- 
nesia and  ammonia).  In  this  way  the  presence  of 
magnesia  may  be  most  certainly  detected. 


RETROSPECT    OF    THE    ALKALINE    EARTHS    (LIME, 
BARYTA,  STRONTIA,  AND  MAGNESIA). 

1.  The  metals  of  the  alkaline  earths  have,   like  the 
alkali-metals,   a  very    great  affinity   for   oxygen;    the 
preparation  of  them  is  exceedingly  difficult. 

2.  Their  oxides  are  called  alkaline  earths; — earths, 
because  they  are  sparingly  soluble;  alkaline,  because 
they  have  a  basic  reaction.      (The  alkalies  are   easily 
soluble.) 

3.  The  alkaline  earths  are,  next  to  the  alkalies,  the 
strongest  bases. 

4.  The  alkaline  earths  have  a  caustic  action,  but  far 
less  than  the  alkalies ;  hence  the  terms  caustic  lime  and 
caustic  baryta. 

5.  They  likewise  eagerly  absorb  carbonic  acid  from 
the  air. 

6.  The  carbonates  of  the  alkaline  earths   are  quite 

24* 


282  METALS  OF  THE  EARTHS. 

insoluble  in  water  (the  carbonates  of  the  alkalies  are 
easily  soluble). 

7.  The  carbonates  of  the  alkaline  earths  lose  their 
carbonic  acid  by  exposure  to  a  powerful  heat  (the  alkalies 
do  not). 

8.  The  alkaline  earths  form  with  fats  insoluble  soap 
(the  alkalies  soluble  soap).  / 


THIRD  GROUP:  METALS  OF  THE  EARTHS. 

ALUMINUM  (Al). 
At.Wt.  =  171.  —  Sp.  Gr.?. 

Clay  and  Loam. 

252.  The  peculiar  action  of  clay  on  being  mixed 
with  water  is  familiar  to  every  one,  forming  with  it  a 
compact,  ductile  mass,  which  may  be  kneaded  into  any 
shape;  it  is  plastic  or  flexible.  If  a  mixture  of  lime 
and  sand  is  treated  in  the  same  manner,  it  will  not  co- 
here, but  remain  friable.  Common  clay  contains  more 
sand  than  plastic  clay,  and,  owing  to  the  presence  of 
iron  ochre,  has  a  yellow  or  brown  color.  There  is 
still  a  coarser  variety  of  clay,  mixed  with  still  more 
sand,  commonly  called  loam. 

Experiment.  —  Hollow  out  a  piece  of  clay,  and  pour 
Fig  133  some   water    into   the 

cavity  thus  formed ;  the 
water  will  not  percolate 
through  the  clay,  as  it 
would  through  sand  or 

lime.  When  beds  of  clay  exist  beneath  the  soil,  the 
rain  is  unable  to  penetrate  far  down  in  those  places, 
and  consequently  bogs  and  marshes  are  formed.  These 


ALUMINUM.  28J 

may  be  drained  by  boring  holes  through  the  clay-beds, 
down  to  a  looser .  layer  of  earth,  through  which  tho 
water  can  flow  off. 

There  are  found  in  many  places  in  the  interior  of  the 
earth  alternate  beds  of  clay  and  silica,  or  sand,  one 


Fig.  134. 


above  the  other.  If  these  strata  ascend  on  each  side, 
forming  hills,  the  rain-water,  as  it  runs  down,  must  col- 
lect between  the  layers  of  clay,  and  rise  in  them  as  in  a 
tube,  since  it  cannot  find  a  vent  in  any  direction.  If, 
in  such  a  geological  formation,  a  low  situation  be  se- 
lected for  boring  through  the  upper  strata  of  clay,  the 
water  will  be  forced  oat  above  the  surface  of  the  soil, 
and  a  natural  fountain  will  be  the  consequence,  from 
which  the  water  will  be  forced  still  higher  on  boring 
through  the  second  layer  of  clay.  These  fountains  are 
called  Artesian  wells,  from  the  province  of  Artois,  in 
France,  where  the  nature  of  the  soil  is  peculiarly  adapt- 
ed to  such  works. 

Experiment.  —  Put  on  a  paper  filter  half  an  ounce 
of  dry  pulverized  clay,  arid  on  another  half  an  ounce 
oi  sand  ;  pour  water  over  each,  and  weigh  them  as  soon 
as  the  filtration  has  ceased ;  the  clay  will  weigh  three 
eighths  of  an  ounce,  and  the  sand  only  one  eighth  of 
an  ounce  more  than  before.  If  the  sand  had  been  very 


284  METALS   Of    THE   EARTH*. 

coarse,  its  increase  of  weight  would  have  been  sliJi 
Clay  is,  indeed,  insoluble  in  water,  but,  like  a  sponge,  it 
can  imbibe  and  retain  a  large  quantity  of  it ;  it  has  a 
very  great  capacity  of  retaining  water.  In  consequence 
of  this  property,  it  also  parts  with  water  again  much 
more  slowly  than  sand  does,  as  may  be  easily  seen  it 
you  put  both  filters  in  a  warm  place  to  dry.  These 
two  species  of  earths  exhibit,  when  dry,  a  s+ill  greater 
difference :  the  clay  forms  solid,  hard  lumps,  the  sand 
remains  a  loose,  granular  powder. 

253.  Experiment.  —  If  you  digest  some  clay  in  an 
infusion   of  logwood  (§  174),   the   clay  acquires,  after 
standing  some  hours,  a  violet  color,  and  the  liquid  be- 
comes   much    more    transparent.       The    clay    has   the 
power  of  absorbing-  coloring-  matter,  and  rendering  it  in- 
soluble.    Potters'  clay,  or  pipe-clay,  conports  itself  in 
the  same   manner   towards  unctuous  substances,  and 
hence  it  is  much  used  for  extracting  grease-spots  from 
wood,  paper,  &c.,  by  spreading  it   over  their  surface, 
and   letting  it  remain   one  or   more  days   in   contact 
with  them.     A   soft   variety  of  clay   is   employed   in 
cloth   factories,  under  the  name   of  fuller's  earth,  for 
removing  again  the  grease  applied  to  the  wool  in  spin- 
ning. 

254.  Experiment.  —  Expose    half  an  ounce  of  thor 
oughly  dried  clay  to  the  air  for  some  weeks,  when  it 
will  be  found  to  have  gained  in  weight.     This  increase 
of  weight  can  only  proceed  from  the  substances  which 
it  has  absorbed  from  the  air ;  these  are  water,  carbonic 
acid,  and  ammonia.     Of  the  presence  of  the  ammonia 
you  may  easily  be  convinced  by  the  smell,   or  if  you 
triturate  a  piece  of  clay  taken  from  an  old  wall,  in  the 
vicinity  of  barns  especially,  with  some  lime  and  a  few 
drops  of  water.     Clay,  when  freshly  dug,  diffuses  no 


ALUMINUM.  285 

odor  of  ammonia,  or  only  a  very  slight  odor,  on  being 
treated  in  the  same  manner.  Thus  is  explained,  also, 
the  peculiar  smell  which  you  perceive  in  all  argillaceous 
stones  when  you  breathe  upon  them,  and  by  which  you 
can  readily  determine  whether  clay  is  contained  in  an 
earth  or  'stone..  As  water,  carbonic  acid,  and  ammonia 
are  the  most  important  means  of  nourishment  for 
plants,  it  is  very  obvious  that  clay  must  enhance  the 
fertility  of  the  soil,  because  it  attracts  those  substances 
from  the  air.  That  clay  is  especially  efficacious  which 
has  remained  for  years  in  contact  with  the  air,  since  in 
consequence  of  slow  weathering,  soluble  salts  of  lime 
and  potassa  (nitre,  &c.)  have  formed  in  it. 

For  this  reason,  bricks,  or  clay  fragments  of  old  build- 
ings, are  valued  by  the  experienced  farmer  as  excellent 
manure.  Clay,  when  gently  burnt,  also  experiences  a 
similar  change  (§  258). 


Constituents  of  Arable  Land. 

255.  Clay,  or  loam,  and  sand  form  the  principal  ing-re- 
dtknts  of  our  arable  land;  therefore,  the  knowledge  of 
their  properties  is  of  great  importance  to  the  agricul- 
turalist, since  it  enables  him  to  form  a  judgment  as  to 
the  different  action  of  soils  in  wet  or  dry,  in  cold  or 
hot  weather,  &c.  A  soil  wholly  composed  either  of 
sand  or  of  clay  is  totally  unproductive  ;  but  a  mixture 
of  them  affords  a  fertile  soil.  A  clayey  or  fat  soil  is  too 
compact  and  heavy,  not  allowing  the  roots,  of  the 
smaller  plants  particularly,  sufficient  room  to  spread  ; 
it  is  likewise  so  dense  that  it  wih1  not  allow  of  a  free 
circulation  of  air.  By  showers  of  short  duration  it 
becomes  baked;  that  is,  a  crust  forms  on  the  surface, 
which  prevents  the  water  from  penetrating  into  the 
soil  ;  but  after  long  continued  rains  it  becomes  muddy 


286  METALS  OF  THE  EARTHS. 

and  then  it  allows  the  water  to  evaporate  but  slowiy, 
and  remains  for  a  long  time  wet  and  cold.  A  sandy  or 
lean  soil  suffers  from  the  opposite  disadvantages ;  it 
has  too  little  consistency  and  is  too  porous,  and  there- 
fore does  not  hold  firmly  the  roots  of  the  plants ;  it  is 
easily  raised  up  and  blown  away  by  the  wind  ;  it  per- 
mits the  rain  to  penetrate  too  deeply,  and  afterwards  to 
evaporate  again  too  rapidly.  These  properties  consti- 
tute what  is  called  the  physical  or  external  condition  ol 
the  soil.  It  is  now  evident,  that  the  physical  condition 
of  a  clayey  soil  may  be  ameliorated  by  the  addition  of 
sand,  and  that  of  a  sandy  soil  by  the  addition  of  clay, 
loam,  or  marl. 

256.  Estimation  of  Arable  Soil.  —  Experiment.  —  To 
ascertain  the  relative  amount  of  clay  and  sand  in  a  soil, 
triturate  half  an  ounce  of  it  in  a  mortar  with  some 
water  into  a  uniform  paste.  Dilute  it  with  more  water, 
and  pour  the  turbid  liquid  into  a  tall  glass,  rinsing  out 
with  water  what  remains  in  the  mortar.  On  stand- 
ing, the  earthy  particles  will  settle  to  the  bot- 
tom, according  to  their  different  specific  grSv- 
ities,  first  the  coarse,  then  the  fine  sand,  and 
finally  the  clay  or  loam-;  and  an  approxima- 
tive con  elusion  of  the  comparative  quantity  of 
each  may  be  arrived  at  by  observing  the  dif- 
ferent heights  of  the  layers  of  sand  and  clay. 
This  estimation  may  be  rendered  more  ac- 
curate by  again  disturbing  the  sediment,  and,  after  a 
short  time,  decanting  it  into  another  vessel,  using  the 
precaution,  however,  not  to  decant  the  sand,  which,  on 
account  of  its  greater  weight,  sinks  first  to  the  bottom. 
The  residue  is  again  stirred  up  \vith  water,  and  the  lat- 
ter decanted,  and  these  pio^es?es  tOkUnmed  until  all 
the  clay  is  washed  out  from  tbe  r^and.  WH>,  decant- 


ALUMINUM.  287 

Fig.  136.  •  ing,  hold  a  rod  against  the  rim 

of  the  glass,  so  that  the  liquid 
may  not  be  lost  by  flowing 
down  on  the  outer  surface  of 
the  vessel,  or  else  besmear  the 
rim  with  tallow,  which  will 
likewise  prevent  the  adhesion 
of  the  liquid  to  the  glass.*  The 
sand  is  dried  and  weighed,  and 
the  loss  in  the  original  half-ounce  is  to  be  calculated 
as  clay. 

This  operation,  by  which  light  bodies  are  mechan- 
ically separated  from  heavier  ones,  is  called  elutriation. 
It  is  frequently  employed  to  separate  finely  crushed  ores 
from  the  admixture  of  the  lighter  particles  of  stone  and 
earth. 

The  third  very  important  ingredient  of  arable  soil  is 
lime  (§237),  which  may  be  estimated  in  the  following 
manner. 

Experiment. —  Put  into  a  capacious  flask  half  an  ounce 
of  well-dried  earth  ;  pour  over  it  three  ounces  of  water, 
and  then  add  gradually  half  an  ounce  of  muriatic  acid, 
and  let  it  remain  for  some  hours  in  a  warm  place. 
When  the  effervescence  has  ceased,  pour  the  liquid 
upon  a  filter,  and  wash  the  flask  and  filter  with  some 
ounces  of  warm  water.  Add  ammonia  to  the  yellowish 
filtrate  till  it  has  a  decided  smell  of  it;  the  brown  flaky 
precipitate  which  is  hereby  s'eparated  consists  of  hydrat- 
ed  oxide  of  iron  and  alumina,  which  you  must  remove 
by  a  second  filtration.  The  clear  solution  obtained  is 
then  boiled  in  a  flask,  and  a  concentrated  solution  of 
carbonate  of  ammonia  or  carbonate  of  potassa  is  added, 
as  long  as  any  precipitate  forms.  This  is  carbonate 
of  lime,  which  you  must  collect  on  a  filter,  wash,  dry 


288  METALS  OF  THE  EARTHS. 

Fig.  137  and  weigh.  A  more  simple  method  is 
to  pour  the  contents  of  the  flask  into  a 
graduated  glass  cylinder,  and  determine 
by  measure  the  lime  which  soon  settles  at 
the  bottom.  You  previously  determine 
the  weight  of  a  degree  of  lime,  once  for 
all,  by  dissolving  4,  6,  8,  10,  &c.,  grains  of 
chalk  in  diluted  muriatic  acid,  precipitating 
them  by  carbonate  of  ammonia,  and  then 
marking  the  space  occupied  by  the  pre- 
cipitate in  the  graduated  cylinder.  If  you 
have  more  liquid  than  the  cylinder  holds, 
you  may  either  evaporate  the  liquid,  or 
perform  the  experiment  with  h^lf  the  quantity.  This 
method,  however,  will  not  give  very  accurate  results 
when  the  soil  contains  not  only  lime,  but  also  alumina, 
since  this  is  partially  precipitated  at  the  same  time 
with  the  carbonate  of  lime. 

These  two  simple  tests,  the  mechanical  and  the 
chemical,  deserve  to  be  more  frequently  employed  by 
the  farmer  than  they  actually  are  ;  indeed,  by  means  of 
them,  and  without  any  costly  apparatus  or  much  ex- 
pense of  time,  he  can  make  himself  sufficiently  ac- 
quainted with  the  most  important  constituents  of  his 
different  soils. 

Earthen-  Ware. 

257.  The  plastic  property  of  clay,  together  with  t.iat 
of  hardening'  by  heat,  renders  it  peculiarly  adapted  for 
the  manufacture  of  earthen-ware.  The  clay,  having 
been  more  or  less  purified  by  elutriation  and  kneading, 
is  either  fashioned  by  the  hand  upon  the  potter's  lathe, 
or  formed  by  pressure  in  moulds  into  articles  of  various 
shapes ;  these  are  first  dried  in  the  air,  and  then  baked 


ALUMINUM.  289 

in  furnaces,  until  they  have  become  Hard  like  stone. 
The  clay  contracts  in  drying,  bat  still  more  in  baking ; 
consequently,  earthen-ware  is  smaller  after  being  baked 
than  before.  On  account  of  this  property,  small  cylin- 
ders of  clay  were  formerly  used  for  measuring  high 
temperatures  (Wedgewootfs  pyrometer).  Though 
earthen-ware  ^acquires  by  baking  great  hardness  and 
solidity,  yet  it  still  remains  so  porous  as  to  imbibe 
water,  and  also  to  let  it  sweat  through.  This  fault  is 
remedied  by  covering  the  ware  with  a  vitreous  coating, 
the  so-called  glazing,  which  is  composed  of  the  same 
materials  as  glass  (§  226).  The  most  important  kinds 
of  pottery  are,  — 

a.)  Bricks  and  flower-pots,  made  of  loam  or  coarse 
clay,  mostly  unglazed.  The  brownish-red  color  of  the 
bricks  is  owing  to  the  presence  of  oxide  of  iron. 

b.)  Earthen-ware,  made  of  common  clay,  and  coated 
with  a  glazing  of  litharge  and  clay. 

c.)  Stone-ware  (fine  earthen-ware),  made  of  very 
white  clay,  and  likewise  covered  with  a  glazing  of  li- 
tharge and  clay. 

d.)  Delft-ware,  stone-ware  covered  with  a  glazing, 
which  is  rendered  opaque  and  of  a  milky  whiteness 
(enamel)  by  oxide  of  tin  (white  Dutch  tiles,  &c.). 

e.)  Porcelain  is  made  of  the  finest  clay  (porcelain 
clay  or  kaolin),  with  felspar,  and  baked  till  fusion  com- 
mences ;  the  glazing  consists  of  potassa-glass,  without 
litharge. 

/.)  English  stone-ware  (ordinary  porcelain)  is  made 
of  gray  clay,  not  strongly  baked  ;  the  glazing  is  prepared 
from  common  salt,  which  is  thrown  into  a  hot  pottery 
furnace,  and  consists  of  soda-glass  without  litharge 
(milk-pans,  beer-flagons,  &c.). 

Only  the  verifiable  pigments  (metallic  oxides)  can 
25 


290  METALS  OF  THE  EARTHS. 

be  employed  for  staining  and  ornamenting  the  different 
kinds  of  pottery. 

Composition  of  Clay. 

258.  Experiment.  —  Dry  thoroughly  a  piece  of  white 
clay,  and  expose  it  for  some  hours  to  a  powerful  heat, 
which  is  most  easily  done  on  the  hearth  of  a  heated 
oven ;  then  rub  two  ounces  of  it  to  a  powder  in  a  por- 
celain bowl  with  one   ounce   of  sulphuric  acid;  pour 
upon  the'mixture  one  ounce  of  water,  and  let  it  remain 
some   weeks   in  a  warm   place.     Frequently   stir   the 
mass  during  this  time  with  a  glass  rod.    Finally,  dilute 
it  with  six  ounces  of  boiling  water,  and  strain  it  through 
linen.     The  residue  on  the  latter  consists  principally  of 
silicic  acid,  but  a  base  called  alumina  (A^  OJ  is  found 
dissolved  in  the  liquid. 

Clay  is,  accordingly,  an  insoluble  salt,  silicate  of 
alumina.  Before  the  clay  is  heated,  the  silicic  acid 
holds  on  so  firmly  to  the  base  that  the  sulphuric  acid  is 
not  able  to  expel  it ;  but  it  can  do  this  after  the  clay 
has  been  moderately  heated.  All  clay  (and  loam) 
contains,  besides  silicate  of  alumina,  variable  quantities 
of  silicates  of  potassa,  soda,  lime,  &c.,  which  are 
likewise  rendered  dissolvable  by  burning  the  clay.  To 
these  alkalies,  as  well  as  to  the  greater  porosity  of  the 
heated  clay,  it  is  to  be  attributed  that  a  heavy  clayey 
soil,  which  is  impervious  to  the  air,  is  converted  merely 
by  burning  into  very  fertile  arable  land,  and  that  badly 
(slightly)  burnt  bricks  yield  a  very  efficient  material  for 
manure. 

Sulphate  of  Alumina  (A12  O3,  3  SO3  +  18  HO). 

259.  Experiment.  —  Evaporate  the  liquid  obtained  in 
the  former  experiment  till  only  one  and  a  half  or  two 


ALUMINUM. 


291 


ounces  of  it  remain,  and  then  put  it  in  a  cool  place  ; 
it  will  crystallize  in  thin  silky  plates  of  a  pearly  lustre, 
which  are  very  deliquescent  ;  it  is  sulphate  of  alumina. 
Pour  off  the  liquor  remaining  behind,  which  always 
contains  free  sulphuric  acid,  and  again  dissolve  the 
crystals  in  a  .fettle  water.  In  factories  the  solution  is 
frequently  evaporated  to  dryness,  and  a  solid  mass  is 
thereby  obtained,  which  is  employed  ih  calico-printing 
and  dyeing. 

Alumina,  or  Oxide  of  -Aluminum  (Alg  O3). 


Al  .  O,  3 SO,,    ^  3 (NaO,  SO. 


Volatile. 


soluble. 


260.  Experiment.  —  Add  a  solution  of  carbonate  of 
soda  to  half  of  the  above  solution  of  sulphate  of  alumi- 
na, until  the  liquid  reacts  basically  ;  a  brisk  efferves- 

cence ensues,  and 
a  gelatinous  pre- 
cipitate is  formed, 
which,  after  repeat- 
ed washings  with 
insoluble,  water,  will  dry  in  a 
warm  place  into  a 
white  powder.  This  powder  is  a  combination  of  alu- 
mina with  water,  hydrate  of  alumina  (A12  O3,  3  H  O). 
It  is  insoluble  in  water,  and  cannot  combine,  like  the 
bases  previously  considered,  with  carbonic  acid  ;  hence 
the  carbonic  acid  gas,  set  free  from  the  carbonate  of 
soda,  escapes  with  effervescence.  Alumina  differs  from 
clay  in  not  being  rendered  plastic  by  water,  and  from 
lime,  baryta,  strontia,  and  magnesia  in  not  giving  an 
alkaline  reaction. 

The  constituents  of  alumina  are  aluminum  and  oxy- 
gen, consisting  of  one  atom  of  aluminum  and  one  and 
a  half  of  oxygen.  Such  bases  are  called  sesquibases  to 
distinguish  them  from  the  simple  bases,  hitherto  consid- 


292  METALS  OF  TFE  EARTHS. 

ered,  as  K  O,  Na  O,  Ca  O,  &c.  The  numbers  of  these 
sesquibases  are  doubled,  in  order  to  avoid  the  inconven- 
ience of  using  fractions ;  thus  1 :  1|  : :  2 : 3,  =  Ala  O3. 

Experiment.  —  Heat  in  a  test-tube  some  alumina 
with  potassa;  it  dissolves  in  it  completely,  since  it  enters 
into  combination  with  the  potassa.  We  call  alumina  a 
base,  because  it  combines  with  acids  ;  we  may  also  re- 
gard it  as  an  acid,  for  it  combines  also  with  bases.  We 
shall  hereafter  find  among  the  metallic  oxides  other 
such  irresolute,  double-faced  characters,  which  play  the 
part  of  a  base  towards  strong  acids,  and  of  an  acid  to- 
wards strong  bases.  Striving  to  be  both,  they  are  in 
reality  neither,  and  therefore  salts  with  an  alumina 
base  always  have  an  acid  reaction,  and  those  with  an 
alumina  acid  a  basic  reaction,  but  both  of  them  are  very 
easily  decomposed. 

Alumina  is  a  body  of  extremely  difficult  fusibility  ;  we 
can  only  melt  small  quantities  of  it  before  the  oxy- 
hydrogen  blow-pipe.  The  melted  alumina  has  the  ap- 
pearance of  glass,  and  a  hardness  which  is  only  sur- 
passed by  that  of  the  diamond  (artificial  rubies).  In 
this  form  we  find  alumina  also  in  nature ;  the  ruby,  the 
most  costly  red  precious  stone,  and  the  sapphire,  the 
most  costly  blue  stone,  consist  of  crystallized  alumina. 
Emery  has  also  the  same  constitution,  and  is  employed, 
on  account  of  its  hardness,  for  polishing  metals  and 
glass. 

Alum   ( Sulphate  of  Alumina  and  Potassa). 
(KO,  SO3  +  A1,O3,  3SO3  +  24HO.) 

261.  Experiment. —  Saturate  two  ounces  of  boiling 
water  with  sulphate  of  potassa,  and  add  to  it  a  solution 
of  sulphate  of  alumina,  obtained  at  §  259.  Stir  the  mix- 
ture till  it  is  cold,  and  decant  the  clear  liquor  from  the 


ALUMINUM.  295 

white  sediment.  The  sediment  is  alum  in  a  state  of 
powder.  If  dissolved  in  boiling  water  and  slowly 
cooled,  you  obtain  from  it  crystallized  alum  in  beauti- 
ful, transparent,  four-sided  double  pyramids  (octahe- 
drons). 

Thus  alumjs  a  combination  of  two  different  salts,—* 
it  is  a  double  salt.  The  two  salts, 
sulphate  of  potassa  and  sulphate 
of  alumina,  have  united  chemi- 
cally together,  for  a  new  body 
with  new  properties  is  formed 
from  them ;  they  have  united 
chemically  with  each  other,  for 
definite  quantities  of  both  salts 
have  entered  into  combination, 

namely,  half  an  ounce 'of  sulphate  of  potassa,  and  an 
ounce  of  sulphate  of  alumina;  or,  more  accurately, 
1  at.  K  O,  S  O3,  and  1  at.  AL,  O3,  3  S  O3.  Alum  is  diffi- 
cultly soluble  in  cold  water,  easily  so  in  hot  water,  has 
an  acid  reaction,  and,  like  all  the  salts  of  alumina,  has 
an  astringent  taste. 

262.  'Experiments  with  Alum. 

Experiment  a.  —  Heat  a  small  crystal  of  alum  before 
the  blow-pipe ;  it  foams  and  melts,  forming  a  white 
porous  mass  (burnt  alum),  the  foaming  is  owing  to  the 
evaporation  of  the  water  of  crystallization,  which  con- 
stitutes nearly  one  half  of  the  weight  of  the  alum. 

Experiment  b. —  Hydrate  of  alumina  is  precipitated 
by  carbonate  of  soda  from  alum,  in  the  same  manner 
as  from  sulphate  of  alumina. 

Experiment  c.  —  Boil  half  an  ounce  of  Brazil-wood 
for  fifteen  minutes,  in  six  ounces  of  water ;  decant  the 
decoction,  and  dissolve  in  it  half  an  ounce  of  alum ;  it 
25* 


294  METALS    OF    THE    EARTHS. 

thereby  acquires  a  more  brilliant  red  color.  Now  add 
to  it  a  solution  of  carbonate  of  potassa  or  of  soda,  as 
long  as  any  precipitate  is  produced ;  this  precipitate 
is  of  a  fine  red  color,  and,  when  dried,  constitutes  the 
Brazil-wood  lake  of  commerce.  In  a  similar  manner 
colored  precipitates  (lakes)  are  obtained  from  other  veg- 
etable coloring-substances.  This  example  serves  to 
show  the  powerful  attraction  which  alumina  has  for 
coloring1  matter.  Almost  all  colors  of  the  animal  and 
vegetable  kingdom  may  be  precipitated  by  alumina* 
from  their  solutions,  which  accounts  for  the  great  im- 
•portance  of  the  alumina  salts  in  dyeing  and  calico- 
printing.  For  this  purpose  the  acetate  of  alumina  is 
very  frequently  substituted  for  alum,  because  the  feeble 
acetic  acid  more  readily  leaves  the  alumina  than  the 
strong  sulphuric  acid  does.  It  is  obtained  by  mixing 
together  a  solution  of  acetate  of  lead  and  sulphate  of 
alumina  (or  alum),  whereby,  by  double  elective  affinity, 
soluble  acetate  of  alumina  (alum  mordant)  and  insoluble 
sulphate  of  lead  are  formed. 

Experiment  d.  —  Moisten  a  piece  of  alum  (or  clay  or 
alumina)  with  a  drop  of  a  solution  of  nitrate  of  cobalt, 
and  heat  it  before  the  blow-pipe;  the  nitric  acid  is 
driven  off,  but  the  oxide  of  cobalt  which  remains  be- 
hind imparts  a  beautiful  blue  color  to  the  compound  of 
alumina.  This  fact  is  frequently  taken  advantage 
of  as  very  accurate  mean's  of  detecting  alumina.  By 
a  similar  process,  a  valuable  and  very  beautiful  blue 
pigment  is  prepared,  called  smalts. 

Another  splendid  blue  pigment,  ultramarine,  has  been 
matfe  within  a  few  years,  by  heating  to  redness  a  mix- 
ture of  alumina,  sulphuret  of  sodium,  and  a  trace  of 
iron.  This  pigment  must  be  carefully  kept  from  con- 
tact with  acids,  as  they  would  evolve  from  it  sulphu- 
retted hydrogen,  and  destroy  the  color. 


ALUMINUM. 

263.  Alum  is  not  prepared  on  a  large  scale  directly 
from  clay  and  sulphuric  acid,  but  from  rocks  contain- 
ing alumina  and  also   sulphur  (pyrites) ;  for  instance, 
aluminous  slates  or  shales.     If  these  rocks  are  allowed 
to  remain  for  some  time  exposed  to  the  air  (weather- 
ing),  or  are  moderately  heated  (roasted),  there  is  formed 
from  the  sulphur  sulphuric  acid,  which  now  combines 
with  the  alumina. 

264.  Alum  affords  a  fine  example  for  elucidating  the 
principle  of  so-called  isomorphism.     For  instance,   we 
are   able   to   replace  the  potassa  in  the  alum  by  an- 
other simple  atomic  base,  namely,  soda  or  ammonia, 
or  to  replace  the  alumina  by  another  sesquibase,  name- 
ly, sesquioxide    of  chromium,  or  sesquioxide  'of  iron, 
\vilhout   thereby  changing    the    octahedral    crystalline 
form.     We  thus  obtain  the  following  kinds  of  alum  :  — 

Potassa  alum,  consisting  of  sulphate  of  alumina    -f-  sulphate  of  potassa. 
Soda  alum,  "  -f         "        "soda. 

Ammonia  alum,        "         ,       "  "          -f-        "        "  ammonia. 

Chrome  alum,  "  sulphate  of  chrome     -\-        "        "  potassa 

(soda  or  ammonia). 
Iron  alum,  "  sulphate  of  iron       -J-  sulphate  of  potassa 

(soda  or  ammonia). 

These  combinations  are  said  to  be  isomorphous  (from 
to-os,  equal,  and  pop^  form),  or  having  the  same  form, 
because  they  possess  a  similar  constitution  and  the 
same  crystalline  form  (octahedron).  The  term  alum  is 
now  applied,  also,  to  some  of  the  double  salts,  in  which 
no  alumina  is  present.  The  three  first  of  the  alums 
mentioned,  have  a  white  color,  chrome  alum,  a  deep 
red,  and  iron  alum,  a  pale  violet  color.  They  may 
easily  be  prepared  by  dissolving  together  in  water  theii 
simple  constituent  salts,  in  proper  proportions,  and 
putting  the  solution  aside  to  crystallize. 


296  METALS    OF    THE     EARTHS. 

Occurrence  of  Alumina  in  Nature. 

265.  Next  to  silica,  alumina  occurs  most  frequently 
in  nature,  and,  indeed,  not  only  in  clay  and  loam,  but 
also  in  rocks  and  minerals ;  for  instance,  in   the  well- 
known  gray-colored  clay-slate,  porphyry,  &c.     Felspar 
must  be  regarded  as  the  most  important  of  the  alumina 
minerals,  and  is  found  in   greater  or   less  quantity  in 
granite,  gneiss,  mica-slate,  and  other  rocks.     In  its  con- 
stitution it  has  the  greatest  similarity  to  alum,  except 
that  it  contains  silicic,  instead  of  sulphuric,  acid. 

Alum  (anhydrous)  (K  O,  S  O3  +  AL,  O3,  3  S  O3) ; 
Felspar  (K  O,  Si  O3  +  AL,  O3,  3  Si  O3). 

Felspar,  like  all  other  stones,  is  finally  disintegrated  by 
the  influence  of  air  and  water,  and  by  heat  and  cold ;  it 
weathers,  as  the  miners  say,  or  is  dissolved,  and  the  sili- 
cate of  potassa  is  thereby  gradually  removed  by  the 
water,  so  that,  as  the  result  of  this  decomposition,  clay 
or  loam  remains  behind  (A12  O3,  3  Si  O3).  When  the 
farmer  lets  his  ploughed  land  lie  fallow,  that  is,  remain 
uncultivated  for  some  time,  he  by  this  means  acceler- 
ates the  weathering ;  soluble  salts  of  potassa,  soda,  lime, 
and  other  salts,  are  thereby  formed  from  the  constitu- 
ents of  the  soil,  and  to  these  salts  especially  is  to  be  at- 
tributed the  greater  fertility  of  fallow  land  over  that 
which  has  been  exhausted  by  cultivation. 

266.  Glucinum,  Yttrium,  Zirconium,  Thorium,  and 
the  recently  discovered  Erbium,  Terbium,  and  Norium, 
are  very  rare  elements,  the  combinations  of  which  with 
oxygen  are  white,  insoluble,  and  earthy,  like  aluminum, 
and  are  called  Glucina,  Yttria,  Zirconia,  &c. 


RETROSPECT  297 

RETROSPECT  OF  THE  EARTHS  'ALUMINA,  &c.)- 

1.  The  earths  are  combinations  of  the  metals  of  the 
earths  with  oxygen. 

2.  They  are  entirely  insoluble  in  water. 

3.  Thpy  do  not  combine  with  carbonic  acid. 

4.  The  most  important  of  these  earths  is  alumina, 
which,  combined  with  silica  (clay,  loam),  forms  a  prin- 
cipal ingredient  of  arable  land,  and  of  many  kinds  of 
rocks. 

5.  Alumina  is  a  much  weaker  base  than  the  alkalies 
and  alkaline  earths. 

6.  Weak  bases,  as  if  they  were  acids,  combine  with 
strong  bases. 

7.  Many  bodies  may,  in  chemical  combinations,  re- 
place another  body,  atom  for  atom,  without  a  change 
of  the  crystalline  form  taking  place  (isomorphous  sub- 
stances). 

8.  Neutral  salts  are  salts  in  which,  for  every  atom  of 
oxygen  which  the  base  contains,  there  is  an  atom  of 
acid. 

9.  Many  neutral  salts  may  combine  with  one  or  sev- 
eral atoms  of  acids ;  such  combinations  are  called  acid 
salts. 

10.  There  are  also  combinations  of  neutral  salts  with 
one  or  more  atoms  of  bases ;  they  are  termed  basic  salts. 

11.  When  two  different  salts  unite  chemically  with 
each  other,  they  are  called  double  salts. 

RETROSPECT  OF  THE  (LIGHT)  METALS  HITHERTO 
CONSIDERED. 

1.  The  metals  of  the  alkalies,  of  the  alkaline  earths 
and  of  the  earths,  are  called  light  metals,  because  they 
are  specifically  lighter  than  the  other  metals 


298  CHEMICAL    PROPORTIONS. 

2.  They  never  occur  in  nature  as  pure  metals,  neither 
as  pure  oxides  (with  the  exception  of  alumina),  but  al- 
ways as  saltS)  and  constitute,  together  with  silica,  the 
principal  portion  of  our  earth. 

3.  Of  all  bodies,  they  have  the  greatest  affinity  foi 
oxygen,  and  form  with  it  oxides,  which  (with  the  excep- 
tion of  the  earths)  dissolve  in  water. 

4.  The  oxides  of  the  metals  of  the  alkalies,  and  ol 
the  alkaline  earths,  are  the   strongest  bases  (alkalies, 
alkaline  earths). 

5.  On  account  of  their  great  affinity  for  oxygen,  the 
preparation  of  the  light  metals  is  very  difficult,  since 
the  combination  between  the  metal  and  oxygen  can 
only  be  destroyed  in  the  strongest  charcoal-fire,  or  by 
the  galvanic  current.     Only   potassium,  sodium,  and 
aluminum  are  as  yet  accurately  known. 

6.  Until  the  year  1807  the  alkalies  and  earths  were 
regarded  as  simple  bodies ;  but  at  that  time  the  English 
chemist,  Davy,  succeeded  in  resolving  them  into  metals 
and  oxygen,  by  means  of  the  galvanic  current. 

7.  Most  of  the  light  metals  are  able  to  decompose 
water,  even  at  ordinary  temperatures,  and  without  the 
aid  of  an  acid;  that  is,  to  withdraw  from  it  the  oxy- 
gm,  and  consequently  liberate  the  hydrogen. 


LAWS   OF   CHEMICAL   COMBINATION. 

BEFORE  proceeding  to  the  consideration  of  the  other 
metals,  it  will  be  well  to  revert  to  the  laws  of  chemical 
combination,  often  mentioned  in  the  foregoing  pages, 
and  to  reduce  them  to  a  methodical  system. 

267.  Classification  of  Chemical  Combinations.  —  As  in- 
numerable words  may  be  formed  from  the  twenty-six 


CHEMICAL    PROPORTIONS.  299 

letters  of  our  alphabet,  so  likewise  innumerable  com- 
pounds may  be  prepared  from  the  sixty -two  chemical 
elements.  These  may  be  classed  into  three  great  di- 
visions. Combinations  of  the  first  order  are  formed 
when  elements  unite  with  elements;  to  this  belong, 
for  instance,  ^acids  and  bases.  When  these  are  com- 
bined together,  we  obtain  combinations  of  the  second 
order,  for  instance,  salts.  From  the  union  of  the  salts 
with  salts  are  produced  combinations  of  the  third  ordert 
for  instance,  double  salts.  We  find  something  quite 
analogous  to  this  in  the  construction  of  our  language. 
From  letters  we  form  syllables,  from  syllables  single 
words,  and  from  single  words  compound  words. 

268.  When  bodies  combine  chemically  with  each  other^ 
it  is  always  in  certain  fixed  and  invariable  proportions. 
Water,  in  whatever  condition  it  may  exist,  whether  in 
springs  or  in  the  sea,  as  ice  or  vapor,  is  uniformly  com- 
posed of  12^  ounces  of  hydrogen   and  100  ounces  of 
oxygen.     When  artificially  prepared  by  burning  hydro- 
gen in  oxygen  gas,  exactly  the  above  proportion  of  each 
gas  is  required,  that  is,  12y  grains,  ounces,  or  pounds  of 
hydrogen  are  required  for  every  100  grains,  ounces,  o» 
pounds  of  oxygen.     If  13  ounces  of  hydrogen  are  take.i, 
half  an  ounce  of  hydrogen  remains  behind ;   or  if  101 
ounces  of  oxygen  are  taken,  then  an  ounce  of  oxygen 
remains  behind.     Quicklime,   whether   prepared   from 
marble  or  limestone,  from  chalk  or  oyster-shells,  invari- 
ably contains  250  ounces  of  calcmm  and  100  ounces  of 
oxygen ;  and  sulphuric  acid,  whether  manufactured  by 
the  Nordhausen  method,  from  green  vitriol,  or  accord- 
ing to  the  English  method,  by  the  combustion  of  sul- 
phur, always  contains  200  ounces  of  sulphur  to  300 
ounces  of  oxygen. 

269.  It  has  also  been  ascertained,  by  the  most  reli- 
able investigations,  how  many  parts  by  weignt  of  the 


300 


CHEMICAL    PROPORTIONS. 


other  elements  combine  with  100  parts  by  weight  of 
oxygen.  Since  these  quantities,  as  will  hereafter  ap- 
pear, are  of  great  importance  in  chemistry,  the  num- 
bers representing  those  of  the  most  common  elements 
are  given,  as  follows  :  — 

100  ounces  of  oxygen,  =  O,  combine  with 


12i  ounces  of  hydrogen, 

orH. 

489  ounces  of  potassium, 

or  K. 

175 

nitrogen, 

"  N. 

290        " 

sodium, 

"  Na. 

75 

carbon, 

"  C. 

225         u 

ammonium, 

"NH4 

200 

sulphur, 

"  S. 

250         " 

calcium, 

"  Ca. 

400 

phosphorus, 

«  p. 

855         " 

barium, 

"  Ba. 

443 

chlorine, 

"  Cl. 

158         " 

magnesium, 

«Mg 

1000 

bromine, 

«  Br. 

171         " 

aluminum, 

"  Ai. 

1586 

iodine, 

"  I. 

350         " 

iron, 

"  Fe. 

325 

cyanogen, 

«Cy. 

345         " 

manganese, 

"  MD 

136 

boron, 

"  B. 

368         " 

cobalt, 

"  Co 

278 

silicon, 

"  Si. 

369         " 

nickel, 

«  Ni 

407 

zinc, 

«  Zn. 

1350         " 

silver, 

"Ag 

735 

tin, 

"  Sn. 

1232         " 

platinum, 

"  Pt. 

294 

lead, 

"  Pb. 

2458         " 

gold, 

"  Au. 

1330 

bismuth, 

"  Bi. 

328         " 

chromium, 

«(* 

396 

copper, 

«  Cu. 

937 

arsenic, 

"  As 

1250                     mercury, 

«  Hg. 

1613         " 

antimony, 

"  Sb 

These  numbers  are  called  combining-  proportionals, 
because  they  express  the  proportion  in  which  an  ele- 
ment chemicall)  combines  with  100  parts  of  oxygen. 
If  we  now  wish  to  ascertain  the  composition  of  po- 
tassa,  or  of  oxide  of  mercury,  we  have  only  to  refer  to 
the  table,  and  we  find,  that  in  potassa  489  ounces  or 
parts  of  potassium  combine  with  100  ounces  or  parts 
of  oxygen,  and  that -in  the  oxide  of  mercury,  1250 
ounces  of  mercury  combine  with  100  ounces  of  oxygen. 

Accordingly,  the  elements  with  the  smaller  propor- 
tional numbers  must  be  regarded  as  more  powerful  than 
those  with  larger  proportional  numbers.  Potassium,  for 
instance,  is  2^  times  stronger  than  mercury,  since  489 
ounces  of  it  unite  with  the  same  quantity  of  oxygen 
that  1250  ounces  of  mercury  do. 


CHEMICAL    PROPORTIONS  301 

270.  Equivalents.  —  Further  experiments  have  led  to 
the  surprising  discovery,  that  these  numbers  not  only 
indicate  in  what  proportion  the  elements  combine  with 
oxygen,  but  also  in  what  quantities  they  combine  with 
each  other.  These  quantities  are  the  same  as  those  of 
the  proportional  numbers.  12^-  ounces  of  hydrogen 
combine  exgfeetly  with  100  ounces  of  oxygen,  forming 
water;  with  200  ounces  of  sulphur,  forming  sulphu- 
retted hydrogen ;  with  443  ounces  of  chlorine,  forming 
muriatic  acid.  The  same  quantity  of  sulphur  which, 
with  300  ounces  of  oxygen,  formed  sulphuric  acid, 
yields,  with  489  ounces  of  potassium,  sulphuret  of  po- 
tassium, with  350  ounces  of  iron,  sulphuret  of  iron, 
and  with  1250  ounces  of  mercury,  sulphuret  of  mer- 
cury (cinnabar).  If  the  iron  is  heated  with  cinnabar, 
the  sulphur  passes  to  the  stronger  iron,  and  the  mer- 
cury is  set  free.  350  ounces  of  iron  are  thus  just  suffi- 
cient to  decompose  1450*  ounces  of  cinnabar,  and  con- 
sequently to  liberate  1250  ounces  of  mercury.  If  more 
iron  is  employed,  a  portion  of  it  remains  uncombined ; 
if  more  cinnabar,  a  part  of  it  remains  undecomposed. 
When  in  a  chemical  combination  one  element  replaces  an- 
other, it  always  happens  in  the  quantities  specified  by  the 
combining  proportionals. 

For  100  dollars  can  be  bought  6  ounces  of  gold. 
or  12  ounces  of  platinum,  or  100  ounces  of  silver,  or 
1,500  ounces  of  mercury;  consequently,  6  ounces  of 
gold  have  the  same  mercantile  value  as  12  ounces  of 
platinum,  or  100  ounces  of  silver,  &c.  The  same  prin- 
ciple holds  good  in  chemistry.  350  ounces  of  iron,  489 
ounces  of  potassium,  or  1250  ounces  of  mercury,  com- 
bine with  100  ounces  of  oxygen ;  accordingly,  350 

*  Cinnabar  is  composed  of  mercury  1250  -f-  sulphur  200  =  1450. 

26 


302  CHEMICAL    PROPORTIONS. 

ounces  of  iron  have  the  same  chemical  value  as  489 
ounces  of  potassium,  or  1250  ounces  of  mercury. 
This  is  the  reason  why  these  numbers  are  likewise 
termed  equivalents  (from  cequus,  equal,  and  valor , 
value).  Thus,  by  one  equivalent  of  oxygen  is  to  be 
understood  100  parts  of  it  by  weight ;  by  one  equivalent 
of  iron,  350  parts  by  weight ;  and  by  one  equivalent  of 
mercury,  1250  parts  by  weight,  &c. 

271.  The  same  law  of  equivalent  proportion  applies 
also  to  the  chemical  combinations  of  the  second  and  third 
order,  to  which  the  process  of  a  neutralization  of  a  base 
jy  an  acid,  and  the  capacity  of  saturation  of  acids,  re- 
ferred (§200).  When  the  basic  properties  of  a  base, 
and  also  the  acid  properties  of  an  acid,  have  disappeared, 
then  these  two  bodies  have  united  with  each  other 
in  precisely  those  quantities  which  are  determined  by 
the  natural  law.  The  amount  of  this  quantity  for  each 
body  may  easily  be  ascertained  by  adding  together  the 
equivalent  numbers  of  their  component  parts. 

Chalk  is  carbonate  of  lime  (Ca  O,  C  OJ. 

Lime  consists  of  Carbonic  Acid  consists  of 

1  eq.  of  calcium  =  250  1  eq.  of  carbon  =    75 

and  1  eq.  of  oxygen  =  100  and  2  eq.  of  oxygen  =  200 

Combining  number  of  Ca  O  =  350  Combining  number  of  C  O*  =  275 

That  is,  in  chalk  350  ounces  of  lime  are  always  com- 
bined with  275  ounces  of  carbonic  acid,  and  exactly  the 
same  proportion  must  be  used  in  the  artificial  prepara- 
tion of  chalk  from  its  constituents.  The  combining 
proportion,  or  equivalent  number,  of  chalk  is  accord- 
ingly =  625. 

If  we  wish  to  convert  chalk  by  common  sulphuric 
acid  into  gypsum  (Ca  O,  S  O0)  we  must  first  seek  for 
the  proportional  number  of  the  acid.  We  commonly 
find  in  it  one  equivalent  of  anhydrous  sulphuric  acid, 
united  with  one  equivalent  of  water. 


CHEMICAL    PROPORTIONS.  303 

The  constituents  of  The  constituents  of 

sulphuric  acid  are  water  are 

1  eq.  sulphur  =  200  1  eq.  hydrogen  =     12j 

and  3  eq.  oxygen  =  300  1  eq.  oxygen      =  100 

E  \.  of  S  03  is  thus    =  500  Eq.  of  H  O  is  thus  =  1 12i 

Consequently,  the  combining  proportion  of  common 
sulphuric  acid  is  612-J-.  This  quantity  just  suffices  tc 
convert  the  above  obtained  625  ounces  of  chalk  intc 
sulphate  of  lime.  The  cartonic  acid  which  thereby 
escapes  amounts  to  275  ounces. 

Gypsum  combines  always  with  two  equivalents  of 
water  of  crystallization;  its  constituents  are,  conse- 
quently, — 

1  eq.  of  Ca  0  =    350 
1  eq.  of  S  O3  =    500 
and  2  eq.  of  H  0    =    225 
Equivalent  number  of  cryst.  gypsum  =  1075  =   CaO,  S  Oa  -{-  2 HO. 

If  you  heat  it,  the  water  is  expelled,  and  there  re- 
mains for  calcined  or  anhydrous  gypsum  the  equiva- 
lent 850.  It  is  evident  that  wate/  enters  into  chemical 
combinations  with  the  acids,  bases,  or  salts,  not  as 
being  essential  to  their  constitution,  but  only  as  form 
ing  a  portion  of  them. 

Previously  to  the  discovery  of  this  law,  hardly  fifty 
ysars  ago,  it  could  only  be  ascertained  by  laborious 
trials  how  much  of  one  body  was  required  to  combine 
with  another,  or  to  replace  another;  it  is  now  only 
necessary  to  refer  to  the  table  of  the  proportional  or 
equivalent  numbers  to  ascertain  beforehand  the  quan- 
tity to  be  employed. 

272.  Multiple  Proportions.  —  Many  elements  have 
the  capacity  of  combining  with  three,  four,  five,  or 
even  more  proportions  of  oxygen,  sulphur,  chlorine, 
&c.,  thus  producing  the  different  oxides,  sulphides, 
chlorides,  &c.,  described  in  section  154.  This  would 


301 


CHEMICAL    PROPORTIONS. 


at  first  seem  to  be  inconsistent  with  the  law  that  bodies 
always  combine  with  each  other  in  fixed  proportions 
but  on  more  mature  consideration  of  the  subject,  it  wiL 
be  obvious  that  no  inconsistency  exists,  and  that  these 
greater  or  less   quantities  are  not  promiscuously  com 
pounded,  but  that  they  are  likewise  combined  in  fixed 
and  invariable  proportions. 

If  we  ascend  a  hill,  it  is  at  our  own  option  to  take 
many  or  few,  long  or  short  steps,  since  the  inclina- 
tion is  not  interrupted  by  perpendicular  acclivities  ; 
but  on  mounting  a  flight  of  stairs  or  a  ladder,  a  deter- 
minate and  regular  number  of  steps  only  can  be  taken. 
In  like  manner,  bodies  which  combine  in  several  propor- 
tions with  another  body  do  so  in  different,  but  yet  in  in- 
variable quantities,  and  such  combinations  always  take 
place  in  ratios  of  1^,  2,  2J-,  3,  or  3-J-,  but  never  in  ratios 
of  !•},  or  If,  or  1-J,  &c.  The  ascent  takes  place,  as  it 
were,  only  by  whole  or  half  steps;  thus,  for  instance,  — 
10°  °Z'  ofx^cn'  carb°nic  oxide  =  C  °" 


75  oz.  of  carbon 
,  .,        -(150   "  "      oxalic  acid  =  C-2O3. 

1  200  «  «      carbonic  acid  =C02. 

f  100  oz.  of  oxygen,  nitrous  oxide  =  N  O. 

75  oz.  of  nitro-  j  200   "  "      nitric  oxide  =  N  O2. 

gen  form,  with  1  300  "  "      nitrous  acid  =  N  O3 

[500   «  "      nitric  acid  =N05. 

f  100  oz.  of  oxygen,  protoxide  of  manganese,  =  Mn  O. 

|  150  "  "      sesquioxide  of  manganese  =  Mn.2  Oa 

a"  <(  200  "  «      hyperoxide  of  manganese  =  Mn  O2. 

nese  form,  with  ,  30Q  „  M      manganic  add  =  MnQj> 

1^350   "  "      permanganic  acid  =  Mna  (^7. 

In  the  combinations  of  carbon,  the  ratio  of 
the  oxygen  is  as  .  .  .  .  1  :  1|  :  2 

In  the  combinations  of  nitrogen,  the  ratio 
of  the  oxygen  is  as  .  .  .  1:2:3:5 

And  in  the  combinations  of  manganese, 
the  ratio  of  the  oxygen  is  as  .  1  :  1J  :  2  :  3  :  3J 


CHEMICAL     PROPORTIONS.  303 

It  is  obvious  that  these  numbers  stand  in  a  very 
simple  ratio  to  each  other,  and  that  the  larger  numbers 
are  a  multiple  of  the  smaller  number;  this  is  expressed 
by  calling  it  the  law  of  multiple  proportions. 

273.  Gaseous  bodies  always  combine  with  each  other  in 
certain  volume^.     The  volume  of  the  gases  is  very  often 
less,  after  combination,  than  the  sum  of  their  volumes 
in  their  separate  state. 

Examples. 

From  1  vol.  of  chlorine  and  1  vol.  of  hydrogen  are 
formed  2  vols.  of  hydrochloric  acid  gas. 

From  2  vols.  of  hydrogen  and  1  vol.  of  oxygen  are 
formed  2  vols.  of  aqueous  vapor. 

From  3  vols.  of  hydrogen  and  1  vol.  of  nitrogen  are 
formed  2  vols.  of  ammoniacal  gas. 

From  6  vols.  of  hydrogen  and  1  vol.  of  sulphur  are 
formed  6  vols.  of  sulphuretted  hydrogen  gas. 

Thus  the  same  constancy  characterizes  the  combi- 
•nations  by  volumes  as  those  by  weight,  and  they  are 
marked  by  a  still  greater  simplicity.  And  if  it  were 
possible  to  convert  all  bodies  into  gases,  probably  a 
similar  simple  proportion  by  measure  or  volume  would 
be  observed  in  all  chemical  combinations. 

274.  Atoms.  —  After  having  proved  by  a  vast  number 
of  facts,  the  result  of  the  most  laborious  investigations, 
that  chemical  combinations  always  take  place  accord- 
ing to  fixed  volumes  and  weights,  the  cause  of  this 
wonderful   immutability   is    sought   for.      A    thinking 
man,  when  he  knows  that  a  thing  happens,  and  how  it 
happens,  will  always  inquire,   Why  is  it  thus,  and  not 
otherwise  ?     This  question  could  not  be  solved  by  any 
effort  of  experiment  and  observation  ;  but  reflection  haa 
enabled  us  to  arrive  at  an  idea  by  which  we  can  ex- 

26* 


306 


CHEMICAL     PROPORTIONS. 


plain  to  ourselves  this  regularity  and  unchangeable- 
ness.  This  idea  has  received  the  name  of  the  atomic 
theory.  It  is  as  follows :  — 

1.)  Every  substance  is  composed  of  small  particles., 
which  lie  in  contact  with  each  other,  and  are  called 
atoms;  between  these  atoms  there  are  interstices  01 
pores.  In  light  bodies  the  atoms  are  more  remote  from 
each'  other,  and  the  interstices  are  larger,  than  in  heavy 
bodies.  When  substances  are  subjected  to  cold  01 
pressure,  the  atoms  approximate  more  closely,  and  the 
bodies  become  denser  and  specifically  heavier,  while, 
if  heated,  the  atoms  separate  from  each  other,  the  pores 
become  larger,  and  the  bodies  consequently  more  ex- 
panded and  specifically  lighter.  The  atoms  are  farthest 
distant  from  each  other  in  gases  and  vapors  ;  in  steam, 
for  instance,  they  are  1700  times  more  remote  than  in 
the  liquid  water,  since  the  former  occupies  1700  times 
more  space  than  the  latter. 

2.)  Simple  bodies  have  simple  atoms,  compound 
bodies  compound  atoms.  For  example,  — 


Carbon : 


Oxygen : 


Calcium : 


Carbonic  oxide ; 


Carbonic  acid 


Carbonate  of  lime : 


Lime: 


3.)  These  small  particles,  of  which  the  mass  of  a  body 
consists,  cannot  be  further  divided  into  yet  smaller  par 


CHEMICAL     PROPORTIONS.  307 

tides.  Thus  is  explained  the  name  atomus  (that  which 
cannot  be  divided). 

4.)  They  are  so  small  that  they  can  neither  be  seen 
nor  counted,  even  by  means  of  the  most  powerful  rnag- 
nifying-glass ;  and  they  have,  therefore,  only  an  imagi- 
nary existence. 

5.)  When  a  solid  body  separates  slowly  from  a  fluid, 
its  atoms  have  time  to  arrange  themselves  beside  each 
other  in  a  definite  manner,  and  we  obtain  regular  crys- 
tals ;  but  on  becoming  suddenly  solid,  an  irregular  dis- 
position of  the  atoms  takes  place,  and  the  body  appears 
amorphous  (vitreous  or  pulverulent). 

6.)  The  position  of  the  atoms  towards  each  other 
may  be  varied.  As  four  balls  may  be  put  in  the  fol- 
lowing positions,  — 


oooo 

so  atoms  also  may  lie  beside  each  other,  arranged 
sometimes  in  one  and  sometimes  in  another  manner 
Thus  is  explained  why  one  and  the  same  substance 
may  often  appear  in  different  forms  of  crystallization, 
or  with  a  different  structure,  consequently  in  two  dif- 
ferent states  (dimorphous).  Sulphur,  at  ordinary  tem- 
peratures, crystallizes  from  its  solutions  in  octahedrons ; 
but  when  fused,  it  crystallizes  on  cooling  in  oblique 
prisms  (§§  125,  126).  A  newly  forged  iron  axle  has  a 
fibrous  texture,  but  after  being  used  for  some  time  its 
texture  becomes  granular. 

7.)   The  atoms  of  different  bodies  have  also  probably 
a  different  size.      A  regular  square  may  be  constructed 


of  four  peas  ;    f~Q~*\  ')U*  if  we  replace  one  of  the  peas 


308  CHEMICAL    PROPORTIONS. 


by  a  bean    i  iy  or    by  a  mustard-seed, 


then  in  both  cases  the  regular  form  is  disturbed ;  it  re- 
mains, however,  unchanged,  when  a  ball  of  lead  of  the 


same   size  as  the  pea  is  substituted  for  it, 


though  the  square  will  now  present  a  different  appear- 
ance. This  is  an  illustration  of  what  occurs  with  the 
atoms.  We  have  seen,  in  the  case  of  the  alums,  that 
the  potassa  may  be  replaced  by  soda  or  ammonia,  or 
the  alumina  by  sesquioxide  of  chromium  or  sesquioxide 
of  iron,  without  changing  the  form  of  the  crystals.  We 
therefore  conclude  that  potassa,  soda,  and  ammonia 
have  equally  large  atoms ;  they  are  isomorphous  (of  the 
same  shape) ;  the  same  applies  also  to  alumina,  and  to 
sesquioxide  of  chromium  and  of  iron.  If  we  see,  on 
the  contrary,  that  a  change  takes  place  in  the  form  of 
the  crystals  when  we  replace  one  body  by  another,  we 
thence  infer  that  there  is  an  unequal  size  of  the  atoms 
in  these  bodies. 

8.)  The  isomeric  state  of  bodies  is  explained  very 
simply  by  the  atomic  theory.  The  most  manifold  and 
regular  grouping  may  be  produced  on  a  chess-board  by 
transposition  of  the  white  and  black  squares ;  for  in- 
stance, — 


CHEMICAL     PROPORTIONS.  309 

Each  figure  is  composed  of  eight  white  and  eight 
black  squares,  but  though  the  absolute  number  is  the 
same,  the  grouping  is  different.  In  a,  one  and  one,  in 
&,  two  and  two,  in  c  and  d,  four  and  four,  squares  are  so 
joined  together  as  to  present  a  different  appearance.  If 
we  imagine  ^hese  squares  to  be  atoms,  we  obtain  an 
idea  of  isomeric  bodies,  and  it  is  thus  rendered  clear 
how  there  may  be  bodies  of  the  same  constitution  and 
form,  yet  presenting  an  entirely  different  appearance, 
and  possessing  different  properties.  Those  exceedingly 
dissimilar  bodies,  caoutchouc  (gum  elastic),  petroleum, 
and  illuminating  gas,  afford  a  striking  example  of  ex- 
ternal difference  and  interior  conformity.  They  have 
the  same  constituents  (carbon  and  hydrogen)  both  in 
quality  and  quantity. 

9.)  The  atoms  of  the  different  bodies  must  finally 
possess  also  weight,  and,  indeed,  very  different  degrees 
of  it.  If  a  piece  of  chalk,  containing  perhaps  a  million 
of  atoms,  has  a  fixed  weight,  so  also  must  the  smallest 
particle  of  it  possess  weight,  however  slight  it  may  be 
for  a  body  having  weight  can  never  be  formed  of  a 
body  having  no  weight.  Chalk  always  contains  350 
ounces  of  lime,  and  275  ounces  of  carbonic  acid.  If  a 
large  piece  of  chalk  has  this  constitution,  so  a  smaller 
piece,  even  the  minutest  particle,  must  unite  in  the 
same  proportions.  If  we  suppose  chalk  to  be  composed 
of  one  atom  of  lime,  and  one  atom  of  carbonic  acid,  we 
ascribe  to  the  atom  of  lime  a  weight  of  350,  and  to  the 
atom  of  carbonic  acid  a  weight  of  275.  In  350  ounces 
of  lime  are  always  contained  250  ounces  of  calcium 
and  100  ounces  of  oxygen ;  this  combination,  also,  is  to 
be  regarded  as  consisting  of  equal  atoms ;  accordingly, 
one  atom  of  calcium  weighs  250,  and  one  atom  of  oxy- 
gen 100.  Finally,  in  275  ounces  of  carbonic  acid  are 


310  HEAVY     METALS. 

always  contained  75  ounces  of  carbon  united  with  200 
ounces  of  oxygen ;  wherefore  75  is  to  be  regarded  as 
the  weight  of  an  atom  of  carbon,  and  200  as  that  of 
two  atoms  of  oxygen. 

The  numbers  are  exactly  the  same  as  those  given  in 
the  list  of  proportional  or  equivalent  numbers.  Thus 
these  numbers  in  an  atomic  point  of  view  may  be  re- 
garded as  the  relative  weight  of  the  atoms ;  hence  the 
third  and  simplest  name  for  them,  atomic  weights. 


HEAVY    METALS. 

FIRST    GROUP    OF   THE    HEAVY   METALS. 

IRON,    FERRUM  (Fe). 
At.  Wt.  =  350.  —  Sp.  Gr.  =  7. 

275.  IF  gold  is  called  the  king  of  metals,  iron  must 
be  deemed  by  far  the  most  important  and  useful  sub- 
ject in  the  metallic  realm.  Iron  was  formerly  regarded 
as  the  symbol  of  war,  and  received  the  name  of  Mars, 
and  the  symbol  $  ;  but  who  does  not  know  that  it  has 
now  attained  also  a  great,  an  indescribably  great  impor- 
tance in  the  peaceable  occupations  of  men  ?  It  is  not 
only  converted  into  swords  and  cannons,  but  into 
ploughshares  and  chisels,  and  into  a  thousand  other 
implements  and  machines,  from  the  simple  coffee-mill 
to  the  wonderful  steam-engine.  It  is  the  ladder  upon 
which  the  arts  and  trades  have  mounted  to  such  an 
extraordinary  height.  It  is  the  bridge  upon  which 
we  now  glide  over  mountains  and  valleys  with  the. 
rapidity  almost  of  magic. 


IRON.  311 

Pure  gold  is  found  on  the  surface  of  the  earth,  and  it 
is  only  necessary  to  free  it  from  earthy  admixtures  to 
obtain  it  in  a  pure  metallic  state.  Not  so  with  iron. 
The  ore  in  which  this  lies  imbedded  must  be  procured 
from  the  earth  by  skilful  operations,  and  its  oxygen  ex- 
pelled by--ingenious  methods,  and  by  exposure  to  the 
hottest  fire,  in  Border  to  convert  it  into  metallic  iron, 
the  latter  must  again  be  fused  and  refined  by  different 
operations  before  it  can  be  forged  and  welded.  Gold  is 
presented  to  men  by  nature  as  a  gift,  but  iron  must  be 
struggled  for  by  the  most  laborious  toil,  by  exertion 
both  of  the  bodily  and  mental  powers.  Thus  iron  has 
become  a  blessing  to  those  countries  whose  inhabitants 
are  occupied  with  the  mining  and  working  of  it;  for,  as 
history  teaches,  in  those  countries  are  found  the  bless- 
ings attendant  on  labor,  health,  contentment,  prosper- 
ity, and  intellectual  culture,  in  a  far  greater  degree  than 
in  those  countries  where  gold  abounds  and  industry  is 
neglected. 

In  another  respect,  also,  iron,  of  all  the  heavy  metals, 
appears  to  be  the  most  important  to  mankind.  It  is 
the  only  metal  which  is  not  injurious  to  the  health,  the 
only  metal  which  forms  a  never-failing  constituent  of 
the  body,  especially  of  the  blood ;  the  only  metal,  finally, 
which  is  found  everywhere  on  the  earth,  in  all  stones 
and  soils,  and  in  almost  every  plant.  Although  we  are 
ignorant  wherein  consists  the  influence  which  it  exer- 
cises upon  the  life  of  animals  and  plants,  yet  its  uni- 
versal diffusion  must  lead  us  to  conclude  that  it  has 
pleased  the  Highest  Wisdom  to  invest  iron  with  an 
importance  for  organic  life  similar  to  that  possessed 
by  common  salt,  lime,  phosphoric  acid,  and  some  other 
substances. 


HEAVY     METALS. 

Experiments  with  Iron  (Iron  Ore). 

276.  For  these  experiments  fine  iron  filings  are  em- 
ployed, such  as  are  kept  in  apothecaries'  shops. 

Experiment  a.  —  Place  17J  grains  of  iron  filings  upon 
a  piece  of  charcoal,  and  heat  it  for  some  minutes  in  the 
flame  of  the  blow-pipe,  directed  upon  one  spot ;  it  be- 
romes  red-hot,  and  the  heat  spreads  throughout  the 
^hole  mass,  as  is  apparent  from  the  iridescent  tints, 

which  precede  the  red 
heat.  The  iron  on  cool- 
ing acquires  a  darker,  al- 
most a  black  color,  and 
bakes  into  a  coherent 
mass  weighing  about 
18|  grains.  Thus,  17J 
grains  have  combined 
with  1J  grains  of  oxy- 
gen. If  you  multiply 
these  numbers  by  20,  you 

obtain  350  grains  of  iron  (1  atom),  and  25  grains  of 
oxygen  (\  atom),  or  four  atoms  of  iron  to  one  atom  of 
oxygen.  This  body  may  be  termed  suboxide  of  iron. 
In  the  protoxide  of  iron,  one  atom  of  iron  (350)  always 
combines  with  one  atom  of  oxygen  (100) ;  consequently 
the  suboxide  may  be  regarded  as  a  mixture  of  one 
atom  of  protoxide  of  iron  and  three  atoms  of  metallic 
iron. 

Experiment  b.  —  Subject  again  the  above  mass  to  a 
red  heat,  for  a  longer  period,  in  the  blow-pipe  flame, 
It  continues  to  increase  in  weight  until  it  has  finally 
gained  from  six  to  seven  grains.  It  now  forms  the 
same  combination  as  was  produced  by  the  burning  of 
iron  in  oxygen,  and  in  the  forging  and  welding  of  iron, 


IRON.  3x3 

namely,  the  well-known  iron  cinders.  It  is  a  mix> 
ture  of  protoxide  and  sesquioxide  of  iron.  The  pro- 
toxide (Fe  O)  cannot  be  prepared  in  a  pure  state  by 
this  method,  as  sesquioxide  is  always  simultaneously 
formed ;  but  from  the  color  of  the  suboxide  and  of  the 
black  oxide,  it  may  be  inferred  that  it  has  a  black  color 
We  perceive  this  color,  also,  in  all  those  rocks  which 
contain  protoxide  of  iron,  generally  in  combination 
with  silicic  acid.  Almost  all  black  and  green  stones, 
for  instance,  basalt,  clay-slate,  greenstone,  serpentine, 
&c.,  owe  their  color  to  protoxide  of  iron. 

An  iron  ore,  which  has  the  same  constitution  and  the 
same  black  color  as  iron  cinders,  occurs  abundantly  in 
many  places.  It  is  called  magnetic  oxide  of  iron,  and  is 
not  only  attractable  by  the  magnetj  but  is  itself  likewise 
magnetic.  A  small  magnet  may  be  prepared  b}  placing 
a  piece  of  magnetic  iron  ore  (loadstone)  between  two 
rods  of  iron,  when  the  magnetic  force  passes  from  the 
stone  into  the  iron.,  The  celebrated  Swedish  iron  is 
mostly  obljained  from  this  variety  of  iron  ore. 

Experiment  c.  —  Iron  cinders,  when  exposed  for  a 
long  time  to  the  exterior  or  oxidizing  blow-pipe  flame, 
become  covered  with  a  red  pulverulent  coating ;  they 
take  yet  more  oxygen  from  the  air,  and  become  sesqui- 
oxide of  iron  (Fe^  O3). 

Experiment  d.  —  The  sesquioxide  of  iron  may  be  pre- 
pared more  easily  in  the  following  manner.  Place  a 
crystal  of  green  vitriol  upon  charcoal,  and  heat  it  until 
it  has  become  of  a  brownish-red  color.  The  water 
and  sulphuric  acid  escape,  and  the  protoxide  of  iron 
(Fe  O)  remaining  behind  absorbs  one  half  as  much 
again  oxygen,  and  becomes  converted  into  sesquioxide 
of  iron  (Fe^Od).  The  red  color  of  the  latter  is  more 
clearly  brought  out  by  rubbing  it  on  paper  with  the 
27 


314 


HEAVY    METALS 


nail.  In  the  same  manner,  sesquioxide  of  iron  remains 
behind  when  green  vitriol  is  heated  in  the  preparation 
of  oil  of  vitriol ;  this  forms  an  article  of  commerce  under 
the  name  of  caput  mortuum,  English  or  polishing  rouge, 
and  is  a  favorite  and  cheap  pigment  for  varnish,  and  is 
also  used  in  the  polishing  of  glass  and  metals. 

Sesquioxide  of  iron  occurs  native  in  many  places 
of  the  earth,  sometimes  crystallized,  as  in  iron-glance ; 
sometimes  compact,  as  in  red  iron-stone ;  or  radiated, 
as  in  red  hematite;  or  earthy,  as  in  -red  ochre.  It  is 
often  also  mixed  with  clay,  and  is  then  called  clay  iron- 
stone. The  coloring  matter  of  red  stones  or  earths  is 
owing  to  the  presence  of  sesquioxide  of  iron.  Many  of 
the  above-named  bodies  form  immense  beds  in  the  in- 
terior of  the  earth,  and  are  used  as  valuable  ores  (spec- 
ular iron)  for  the  manufacture  of  iron. 

Experiment  e.  —  Introduce  some  iron  filings  into  a 
tumbler,  and  fill  it  with  spring-water ;  the  iron  will 
gradually  lose  its  lustre,  and  assume  a  black  color ;  it 
is  converted  into  magnetic  oxide  of  iron.  Repeat  this 
experiment  with  water  that  has  been  boiled ;  in  this, 
the  iron  will  retain  its  metallic  lustre.  The  cause  of 
this  difference  is  owing  to  the  air  and  carbonic  acid, 
which  are  present  in  all  spring-water,  and  slowly  ox- 
idize the  iron.  These  gases  are  expelled  by  boiling, 
therefore  no  oxidation  takes  place  in  water  that  has 
been  boiled. 

Experiment  f.  —  If  you  now  pour  off  the  water,  so 
that  the  iron  comes  in  contact  also  with  the  air,  rust 
begins  to  form  upon  it.  The  iron  absorbs  so  much  ox- 
ygen that  it  becomes  a  sesquioxide ;  it  also  absorbs  a 
definite  quantity  of  water  (3  atoms),  which  may  be  re- 
garded as  the  cause  of  the  yellow  color  of  jpst.  Rust 
is  therefore  hydrated  sesquioxide  of  iron  (Fe,  Oa,  3  H  O). 


IRON, 


315 


If  you  keep  the  iron  moist,  and  stir  it  round  severa, 
times  every  day,  it  will,  after  a  time,  be  completely  con- 
verted into  rust. 

This  combination  frequently  occurs  also  in  nature, 
and  is  used  as  an  excellent  iron  ore,  under  the  name  oi 
brown  iron  ore.  When  mixed  with  clay  it  is  called 
yellow  clay  iron-stone,  yellow  ochre,  &c.  The  yellow  oi 
brown  color  which  we  see  in  so  many  stones  when 
they  are  exposed  to  the  air,  the  yellow  or  brown  color 
of  the  soil,  loam,*or  sand,  always  proceeds  from  the  hy- 
drated  sesquioxide  of  iron.  The  weathering  of  black 
varieties  of  stone  to  a  brown  stratum,  and  finally  to  a 
yellow  arable  soil,  will  now  no  longer  appear  strange ; 
the  black  protoxide  of  iron  contained  in  them  is  grad- 
ually oxidized  into  a  yellow  hydrated  sesquioxide  of 
iron. 

Experiment  g.  —  Put  a  small  quantity  of  the  mag- 
netic oxide  of  iron  obtained  at  b,  or  some  iron  filings, 
into  a  phial ;  fill  the  latter  with  artificial  Seltzer-water, 
and  let  it  stand,  well  stopped  up,  for  one  day.  The 
white  flakes  which  deposit  on  the  bottom  of  the  phial 
are  carbonate  of  the  protoxide  of  iron,  formed  from 
the  protoxide  of  iron  of  the  iron  cinders,  and  from  the 
carbonic  acid  of  the  Seltzer-water.  The  chemically 
combined  water  in  this  case  communicates  a  white 
color  to  the  black  protoxide  of  iron.  The  clear  liquid 
also  contains  some  of  the  carbonate  of  iron  in  solution, 
as  is  evident  from  the  inky  taste  peculiar  to  solutions 
of  iron.  It  is  then  to  be  poured  into  a  tumbler,  and  left 
for  some  time  exposed  to  the  air.  In  proportion  as  the 
free  carbonic  acid  escapes,  the  surface  is  covered  with  a 
delicate  white  pellicle,  the  color  of  which  gradually 
changes  to' yellow,  then  to  red  and  violet;  finally,  the 
pellicle  assumes  a  yellowish-brown  color,  and  falls  aa 


316  HEAVY    METALS. 

rust  to  the  bottom.  Protoxide  of  iron  attracts  oxygen 
with  great  avidity,  and  is  converted  into  magnetic  oxide 
of  iron,  and  finally  into  hydrated  sesquioxide  of  iron. 
The  salts  of  protoxide  of  iron  act  also  in  the  same  man- 
ner;  this  is  the  reason  of  their  becoming  yellow  by  long 
keeping,  or  by  exposure  to  the  air.  A  very  thin  pellicle 
of  magnetic  oxide  of  iron  gives  a  yellow  reflection ;  a 
thicker  pellicle,  a  red  or  brown,  and  a  still  thicker  one, 
a  violet  and  blue  reflection;  this  explains  the  iridescent 
changes  of  color  presenting  such  a  beautiful  appearance 
on  the  surface  of  standing  waters.  In  those  places 
where  spring-waters  flow  over  stones  containing  iron, 
natural  solutions  of  carbonate  of  iron  (chalybeate 
waters)  frequently  occur,  which  are  likewise  decom- 
posed by  the  air.  This  decomposition  of  the  carbonate 
of  iron  is  the  source  of  the  brown  mud  which  is  de- 
posited in  large  quantities  from  some  waters.  By  the 
accumulation  of  this  mud,  large  beds  of  hydrated  ses- 
quioxide of  iron  are  formed,  known  under  the  name 
of  bog-iron  ore,  and  from  which  iron  is  worked.  This 
ore  usually  contains  also  some  phosphoric  acid. 

The  carbonate  of  protoxide  of  iron  is  found  in  many 
countries  in  the  form  of  a  light  gray  massive  stone,  and 
in  such  large  quantities  that  iron  is  obtained  from  it. 
The  famous  Styrian  steel  is  principally  prepared  from 
this  ore,  which  is  called  spathic  iron  ore,  or  spherosid- 
erite.  Mixed  with  clay,  it  very  frequently  occurs  asso- 
ciated with  pit-coal,  and  it  is  from  this  ore  that  most  of 
the  English  iron  is  obtained. 

277.  In  attending  to  the  combinations  which  iron 
yields  with  oxygen,  we  have  also  become  acquainted 
with  the  most  important  iron  ores  from  which  iron  is 
prepared  on  a  large  scale.  They  are  the  following:  — 

Fe  O  -f-  Fea  Oa,  or  magnetic  iron  ore. 


IRON.  317 

Fe  O,  C  Oa,  or  spathic  iron  (clay   iron-stone,  sphe- 

rosiderite). 

Fe^  O0,  or  specular  iron  (red  hematite,  iron-glance,  &c.) 
PQZ  Oj  +  3  H  O,  or  brown  iron  ore  (yellow  iron-stone, 

yellow  ochre,  &c.). 

Cast-iron,  Bar-Iron,  and  Steel. 

278.  Working'  of  Iron.  —  In  order  to  extract  metallic 
iron  from  the  ores  just  mentioned,  they  must  be  de- 
prived of  their  oxygen.  This  is  generally  done  by  ex- 
posing them  with  charcoal  to  a  red  heat.  As  a  general 
rule,  a  mixture  of  several  kinds  of  ore  is  used  for  smelt- 
ing, because  experience  has  taught  that  this  process  is 
then  conducted  more  easily  and  more  completely  than 
when  only  one  kind  of  iron  ore  is  employed.  The  ores, 
containing  carbonic  acid,  water,  or  sulphur,  must  pre- 
viously be  heated  in  appropriate  furnaces  to  expel  these 
volatile  gases  (roasting'  of  the  ores).  It  must  also  be 
borne  in  mind  that  the  iron  ores  are  never  pure,  but 
always  contain  foreign  ingredients  (gangues) ;  for  in- 
stance, silica,  clay,  lime,  manganese,  phosphorus,  &c. 
Silica  especially  forms  a  principal  ingredient  in  iron 
ores.  This  does  not  melt  even,  when  exposed  to  the 
hottest  furnace-fire;  and  yet  it  must  be  melted,  that 
the  iron  may  flow  from  the  ores,  and  be  obtained  as  a 
coherent  mass.  This  is  effected  by  the  addition  of  a 
base,  commonly  lime,  with  which  the  silicic  acid  will 
combine.  A  lime-glass  is  formed,  and  if  loam  or  clay 
be  present  also  arj  alumina-glass,  both  of  which,  when 
combined,  melt  more  readily  than  each  separately,  and 
flow  off  as  slag.  The  substance  which  forms  this 
fusible  compound  is  termed  the  flux;  and  the  combi- 
nation of  the  prepared  ore  and  the  flux  is  called  the 
mixture.  Alternate  layers  of  this  mixture,  and  of  wood- 
27* 


318 


IIKAVY     MKTAL3. 


charcoal  or  of  coke  arc  now  thrown  into  a  large  furnace, 
called  the  blast-furnace,  constructed  as  shown  in  the 
annexed  figure. 

Fig.  140. 


The  portion  a  of  the  blast-furnace  is  called  the  shaft ; 
b  is  the  boshes,  c  is  the  crucible  part,  and  e  is  the  hearth. 
The  mouth  of  the  furnace  serves  both  for  charging  the 
materials,  and  for  the  escape  of  the  smoke ;  it  is  thus 
both  a  door  and  a  chimney.  In  the  upper  portion  of 
the  shaft  the  mixture  is  heated  to  redness  (it  is  roast- 
ed) ;  during  this  process  the  carbonic  acid  of  the  lime- 
stone also  escapes.  Farther  down,  the  charcoal  ab- 
stracts from  the  iron  ore  its  oxygen,  and.  escapes  with 
it  as  carbonic  oxide,  which  at  the  opening  is  entirely 


IRON.  319 

consumed,  on  access  of  air,  into  carbonic  acid,  and  oc- 
casions the  bright  flame  which  issues  from  the  top. 

In  the  boshes,  where  the  greatest  heat  is  evolved,  the 
reduced  iron  melts  and  falls  in  drops  upon  the  hearth, 
together  with  the  silica,  lime,  and  clay ;  these  form  a 
slag,  which  flpats  on  the  molten  iron,  and  is  drawn  off 
at  i.  The  melted  iron  is  suffered  to  flow  off  from  time 
to  time,  by  a  small  opening  made  in  the  side-wall  of  the 
hearth.  After  having  heated  to  a  hundred  degrees  or 
more  the  air  necessary  for  burning  the  charcoal  or  coke, 
it  is  forced  at  d,  by  means  of  large  bellows,  or  other 
wind  apparatus,  into  the  furnace,  in  which  a  heat  of 
perhaps  1200°  or  1400°  C.  may  be  produced.  In  pro- 
portion as  the  melted  iron  and  the  slag  are  removed 
from  beneath,  fresh  charges  of  ore,  lime,  and  charcoal 
are  introduced  at  the  top,  and  in  this  manner  the 
smelting  often  continues  uninterruptedly  for  five  or  six 
years,  according. as  the  furnace  holds  out. 


Iron  Ore, 
Flux, 
Fuel, 

Iron  -f- 

Carbon, 

Oxygen  -f- 
Carbon, 

Silica  (clay). 
Lime  (clay). 

Product, 

Carburetted  Iron 
(cast-iron). 

Carbonic  Oxide  and 
Carbonic  Acid- 

Silicate  of  Lime  and  >  y. 
Silicate  of  Alumina  $      g 

The  slag  from  the  blast  furnaces  has  generally  a 
green  or  blue  color,  owing  to  the  protoxides  of  iron 
and  of  manganese  there  dissolved  in  it.  It  is  fre- 
quently formed  into  square  blocks,  and  used  for  build- 
ing-stones. 

279.  Cast  or  Crude  Iron.  —  The  metal  obtained  by 
the  above  process  is  by  no  means  pure  iron,  but  a 
chemical  mixture  of  iron  and  carbon.  A  hundred- 
weight of  iron  takes  up,  at  the  hottest  white  heat,  from 
about  four  to  five  pounds  of  carbon,  and  likewise  some 
silicon  from  the  silicic  acid,  some  aluminum  from  the 


320  HEAVY    METALS. 

clay,  and  sometimes  also  a  trace  of  sulphur,  phos* 
phorus,  arsenic,  &c.,  when  these  were  contained  in  the 
iron  ore.  Cast-iron,  thus  obtained,  is  characterized  by 
the  following  properties. 

a.)  It  is  fusible  at  a  glowing  white  heat  (wrought- 
iron  and  pure  iron  are  not) ;  therefore  it  is  especially 
adapted  for  those  iron  articles  which  are  made  by  cast- 
ing. For  re  melting  iron  on  a  small  scale,  graphite 
crucibles  are  made  use  of,  but  on  a  large  scale  shaft- 
furnaces  (Schachtofen),  or  the  so-called  cupola-furnaces. 

b.)  Cast-iron  is  brittle,  and  can  neither  be  forged  nor 
welded  (bar-iron  and  steel  may  be  bent,  forged,  and 
welded).  The  application  of  cast-iron  must,  therefore, 
be  limited  to  the  manufacture  of  such  articles  as  are 
not  exposed  to  being  bent,  or  to  strong  concussions. 
Very  recently,  however,  a  method  has  been  discovered 
for  imparting  to  cast-iron  a  certain  degree  of  flexibility, 
and  even  of  malleability,  by  exposing  it  for  several 
days  with  iron  scales  or  spathic  iron  to  a  red  heat. 
The  term  malleable  cast-iron  (fonte  malleable)  has 
been  given  to  this  kind  of  iron. 

There  are  two  kinds  of  cast-iron  in  commerce,  known 
as  gray  and  white  iron.  The  gray  iron  is  almost  black, 
has  a  granular  texture,  and  admits  of  being  filed,  bored, 
&c. ;  the  white  iron,  on  the  contrary,  is  of  a  silvery 
whiteness,  possesses  a  lamellar-crystalline  texture,  and 
is  so  hard  as  not  to  be  acted  upon  by  steel  instruments. 
Crude  white  iron,  by  remelting  and  very  slow  cooling, 
is  changed  to  gray;  on  the  other  hand,  the  gray  is 
changed  to  white  iron  by  being  heated  and  suddenly 
cooled  Gray  iron  is  best  adapted  for  castings ;  white 
iron  is  the  most  suitable  for  the  manufacture  of  bar 
iron  and  steel. 

280.  Malleable   or   Bar  Iron.  —  Cast-iron,  £y  being 


IRON.  321 

deprived  of  its  carbon,  is  converted  into  malleable  iVw, 
and  acquires  the  following  very  important  properties. 

a.)  Bar-iron  possesses  great  ductility  and  tenacity,  and 
may  be  hammered  or  rolled  into  sheets,  and  drawn  out 
into  fine  wire,  which  is  not  the  case  with  cast-iron. 

b.)  At  a  less  degree  of  heat  than  that  of  fusion,  it 
becomes  soft,  like  wax  or  glass,  so  that  two  glowing 
pieces  may  be  welded  into  one.  Upon  this  property 
rests  its  capacity  of  being'  welded,  which  is  possessed  by 
no  other  known  metal,  except  platinum.  Ah1  the  other 
metals  become. fluid  instantaneously,  as  is  the  case  with 
ice,  without  undergoing  previous  softening. 

c.)  Wrought-iron  is  sufficiently  soft  to  be  worked  by 
steel  instruments,  and  it  does  not  become  harder,  if, 
when  heated  to  redness,  it  is  suddenly  quenched  in 
water  (steel  is  thereby  rendered  brittle). 

d.)  Wrought-iron  is  distinguished,  moreover,  from 
cast-iron  by  its  fibrous  texture,  composed,  as  it  were,  of 
threads  incorporated  together;  while  cast-iron  has  the 
appearance  of  being  a  baked  granular  mass.  But  it  is 
a  very  striking  fact  that  fibrous  wrought-iron,  by  re- 
peated jolts  or  blows,  becomes  gradually  granular  and 
brittle,  as,  for  example,  in  the  axletrees  of-  carriages. 
Thus,  also,  in  solid  bodies,  their  particles  or  atoms  can, 
change  their  position  with  regard  to  each  other,  which 
was  formerly  supposed  to  be  possible  only  with  liquid 
bodies.  By  thoroughly  heating  and  reworking,  the 
former  strength  and  flexibility,  as  well  as  the  fibrous 
texture,  is  restored  to  the  iron. 

Wrought-iron  is  not  entirely  freed  from  carbon  ;  it 
contains,  however,  only  from  a  quarter  to  a  half  pound 
of  it  for  each  hundred-weight.  Iron  entirely  free  from 
carbon  is  softer  and  more  tenacious  than  bar-iron ;  thus 
we  see  tha^t  it  is  the  chemical  combination  of  the  car 


322  HEAVY    MI'TALS. 

bon  with  the  iron,  as  in  cast-iron,  which  destroys  these 
two  properties  of  softness  and  tenacity. 

281.  Refinery  of  Iron.  —  1.  Finery  Process. —  The 
method  which  is  employed  for  separating  carbon  from 
the  cast-iron  is  very  simple.  The  carbon  is  burnt  out 
by  heating  the  iron  to  fusion,  and  constantly  stirring  it 
while  exposed  to  a  current  of  air,  the  oxygen  of  which 
combines  with  the  carbon,  forming  carbonic  oxide  gas. 
During  the  operation,  a  considerable  portion  of  the  iron 
(one  quarter)  is  converted  by  oxidation  into  iron  cin- 
ders, which  fuse  with  the  sand,  that  either  adheres  to  the 
cast-iron,  or  is  purposely  strewed  upon  the  hearth,  and 
form  with  it  a  heavy  black  slag  of  silicate  of  magnetic 
oxide  of  iron.  The  iron  mass  becomes  gradually  more 
tenacious,  since  the  iron  melts  so  much  the  more  diffi 
cultly  the  less  carbon  it  contains ;  and  finally,  in  the 
form  of  a  loosely  coherent  mass  (the  bloom)  is  placed 
under  a  loaded  hammer,  by  a  few  blows  of  which  the 
remaining  slag  is  pressed  out,  and  the  iron  particles  are 
formed  into  a  compact  mass.  The  latter  is  afterwards 
usually  hammered  or  rolled  into  bars  or  bands.  This 
method  of  converting  brittle  cast-iron  into  ductile  and 
malleable  iron  is  called  the  finery  process.  The  object 
of  the  refinery  is,  as  has  just  been  shown,  to  separate  the 
Carbon  from  the  iron.  The  annexed  scheme  serves  to 
render  the  process  more  intelligible. 


Cast  Iron, 
Air, 
Sand, 

Iron  |, 

Iron  |, 
Oxygen, 

Silica, 

Carbon. 
Oxygen. 

Vroducts, 

Wrought  Iron, 

Slag, 

Carbonic  Oxide. 

2.  Puddling  Process.  —  For  the  refining  or  decarbon- 
izing of  larger  quantities  of  iron,  the  reverberatory  fur- 
naces are  used,  similar  to  those  employed  in  the  prep- 
aration of  soda  (§  220).  As  in  these  furnaces  the  fue1 


IRON. 


323 


Fi«  14L  does  not  come  in  contact 

with  the  iron  itself,  a 
cheaper  fuel  than  char 
coal  may  be  made  use 
of,  for  instance,  pit-coal 
or  turf,  the  ashes  of 
which,  if  mixed  with 
the  iron,  would  certainly 
spoil  it.  These  are  call- 
ed puddling-furnaceS)  be- 
cause the  iron  must  be 
kept  constantly  stirred 
(puddled). 

282.  Steel.  —  Steel  holds  a  middle  place  between  cast 
and  wrought  iron,  both  as  to  the  quantity  of  carbon  it 
contains,  and  other  properties. 

a.)  If  quenched  when  heated  to  redness,  it  is  ren- 
dered hard  and  brittle  (like  cast-iron) ;  if  cooled  some 
what  more  slowly,  it  is  rendered  elastic,  and  if  cooled 
very  slowly,  it  is  soft,  ductile,  and  malleable  (like  bar- 
iron). 

b.)  It  is  less  fusible  than  cast-iron,  and  more  so  than 
bar-iron. 

c.)  It  contains,  in  every  hundred-weight,  from  two  to 
two  and  a  half  pounds  of  carbon. 

To  these  properties  steel  owes  its  importance  as 
a  material  for  thousands  of  articles,  especially  for  cut- 
ting instruments,  since  it  may  be  made  soft  or  hard, 
elastic  or  brittle,  at  pleasure.  The  article  manufactured 
is  usually  first  heated  to  redness,  then  suddenly  cooled 
by  quenching  it  in  water,  and  afterwards  tempered  in 
order  to  diminish  its  hardness  and  brittleness. 

Experiment.  —  Hold  a  steel  knitting-needle  in  the 
flame  of  a»spirit-lamp  till  it  is  red-hot,  and  then  quickly 


324  HEAVY    METALS. 

plunge  it  in  cold  water ;  it  thereby  becomes  so  brittle 
as  to  break  on  any  attempt  to  bend  it.  Again  hold 
the  needle  in  the  fire,  and  observe  the  changes  of  color 
which  it  passes  through ;  it  will  first  become  yellow, 
then  orange,  crimson,  violet,  blue,  and  finally  dark-gray 
The  cause  of  this  change  of  color  is  the  same  as  that 
of  the  ferruginous  water  (§  276),  namely,  a  film  of  oxide 
forms  upon  the  steel ;  at  first  the  film  is  thin,  and  has 
a  yelloiu  appearance,  but  gradually  it  becomes  thicker 
and  also  darker,  as  the  heat  increases.  The  final  result 
• —  the  dark  gray  coating  —  is  iron  scales.  On  the 
standing  of  the  ferruginous  water  in  the  air,  the  oxida- 
tion advanced  (§276)  a  step  further;  in  that  case,  the 
final  result  was  a  brown  substance,  —  hydrated  sesqui- 
oxide  of  iron.  A  definite  degree  of  hardness  and  elas- 
ticity of  the  steel  corresponds  to  each  of  these  tints,  the 
needle  when  covered  with  the  yellow  film  being  the 
hardest  and  most  brittle,  and  when  presenting  a  blue 
aspect  being  in  its  softest  and  most  elastic  condition. 
The  workmen  in  steel  impart  to  their  articles  various 
degrees  of  hardness  and  elasticity  by  tempering ;  files 
and  razors  are  made  very  hard  and  brittle,  —  saws, 
watch-springs,  &c.,  soft  and  elastic. 

283.  Steel  may  be  prepared  in  various  ways :  — 

1.)  By  partly  refining  cast-iron,  so  that  only  one  half 
of  the  carbon  is  burnt  out  (crude  steel) ;  or 

2.)  By  the  process  of  cementation,  which  consists  in 
filling  an  iron  box  with  bar-iron  and  powdered  char- 
coal, and  then  maintaining  the  whole  for  several  days 
at  a  red  heat.  The  carbon  gradually  penetrates  into 
the  iron,  thus  converting  it  into  steel  (blistered  steel). 

Both  these  kinds  of  steel  must  be  rendered  uniform, 
either  by  repeated  hammering  (tilting)  of  it  when  heat- 
ed to  redness  (tilted  steel),  or  by  remelting  (cast  steel) 


IRON.  325 

Steel  may  be  ornamented  by  corroding  its  polished 
surface  with  acids,  whereby  a  variety  of  light  and 
dark  colored  shades  and  impressions  will  be  pro- 
duced. 

From  the  constituents  of  bar  and  cast  iron  it  may  be 
inferred  that  steel  can  be  made  by  an  intimate  combi- 
nation in  eq%al  proportions  of  those  two  substances. 
In  this  manner,  indeed,  the  exterior  surface  of  wrought- 
iron  articles  —  as,  for  instance,  of  agricultural  imple- 
ments, chains,  &c.  —  can  easily  be  converted  into  steel, 
by  being  heated  in  melted  cast-iron.  This  object  may 
be  attained  more  easily  by  strewing  ferrocyanide  of  po- 
tassium over  the  hot  iron  (§  292). 

Iron,  nickel,  and  cobalt  are  the  only  metals  which 
are  attracted  by  the  magnet.  Magnetism  immediately 
vanishes  from  bar-iron  when  it  is  removed  from  the 
magnet;  while  steel,  on  the  contrary,  retains  its  mag- 
netic power,  and  does  not  lose  it  until  heated  to  red- 
ness (steel  magnet).  The  magnetic  oxide  of  iron  is 
likewise  attracted  by  the  magnet,  owing  to  the  protox- 
ide contained  in  it,  but  the  sesquioxide  of  iron  is  not 
so  attracted. 

Salts  of  Iron. 

284.  The  protoxide  and  sesquioxide  of  iron  «form 
salts  with  acids ;  we  have,  accordingly,  two  series  of 
iron  salts  :  —  a)  the  salts  of  protoxide  of  iron  are  gen- 
erally green,  and  consist  of  one  atom  of  protoxide  of 
iron,  and  one  atom  of  acid ;  b)  the  salts  of  sesquioxide 
of  iron  are  usually  of  a  yellowish-brown  color,  and  con 
sist  of  one  atom  of  oxide  and  an  atom  and  a  half  of 
acid  (or  2:3). 

Iron  and  Acids. 

It  has  already  been  mentioned  (§  173)   that  many 
28 


326  HEAVY     METALS. 

metals  dissolve  only  in  diluted  acids,  others  only  in 
concentrated  acids,  and  that  the  former  take  the  oxy- 
gen requisite  for  their  oxidation  from  the  water,  while 
the  latter  take  it  from  the  acids.  Iron,  together  with 
manganese,  zinc,  cobalt,  nickel,  and  tin,  belongs  to  the 
first-named  class  of  metals,  which  are  called  water-de- 
composing' or  electro-positive  metals.  The  mere  circum- 
stance, that  in  the  presence  of  an  acid  they  are  able  to 
abstract  oxygen  from  the  water,  leads  to  the  supposi- 
tion that  they  are  more  powerful  chemical  bodies  than 
those  metals  which  cannot  do  this.  This  supposition  is 
in  reality  confirmed  ;  the  electro-positive  metals  evince 
a  far  greater  affinity  for  oxygen,  sulphur,  chlorine,  &c., 
and  their  oxides  a  much  greater  affinity  for  the  acids, 
than  is  exhibited  by  the  other  metals  and  their  oxides. 
It  may  be  well  in  this  place  to  remind  the  student  that 
a  solution  of  a  metal  does  not  contain  a  metal  as  such, 
but  always  a  metallic  salt  in  solution  (§  160). 

285.   Green   Vitriol,  or  Sulphate  of  Protoxide  of  Iron 
(Fe  O,  S  O3  +  6  H  O). 

This  salt,  which  is  always  formed  when  iron  is  dis- 
solved in  diluted  sulphuric  acid,  is  often  called  green 
vitriol,  on  account  of  its  pale-green  color.  By  slowly 
evaporating  the  solution,  the  salt  may  easily  be  ob- 
tained in  oblique  rhomboidal  prisms ;  these  crystals 
contain  nearly  one  half  their  weight  of  water  of  crys- 
tallization. 

Experiment.  —  Dissolve  100  grains  of  blue  vitriol 
(§  175)  in  an  ounce  of  water,  and  introduce  into  the 
solution  a  piece  of  polished  iron,  which  has  been  previ- 
ously weighed  ;  the  blue  color  will  gradually  change  to 
green,  while  the  iron  is  covered  with  a  red  coating  of 
copper.  The  stronger  iron  takes  from  the  copper  its 


IRON. 


327 


oxygen  and  sulphuric  acid,  and  combines  with  both  of 

them;  32  grains  of  me- 
tallic copper  are  de- 
posited, while  full  28 
grains  of  iron  have  been 
insoluble,  dissolved.  But  32  is  to 
28  nearly  as  396  (the 
atomic  weight  of  copper)  is  to  350  (the  atomic 
weight  of  iron) ;  accordingly,  one  atom  of  copper  is  re- 
placed by  one  atom  of  iron.  This  process  is  called  the 
reduction  of  a  metal  by  the  moist  way.  The  supernatant 
liquor  contains  in  solution  no  longer  any  copper,  but 
only  green  vitriol,  which  may  be  crystallized  by  evap- 
oration. Thus  is  explained  the  inappropriate  name  of 
copperas,  very  commonly  applied  to  sulphate  of  iron. 

Experiments  with   Green   Vitriol. 

Experiment  a.  —  Let  a  solution  of  green  vitriol  stand 
for  some  time  in  the  air ;  it  will  gradually  assume  a  yel- 
lowish color,  and  a  brownish-yellow  substance,  hydrat- 
ed  sesquioxide  of  iron,  is  deposited.  All  the  other  salts 
of  protoxide  of  iron  do  the  same  ;  namely,  they  attract 
oxygen  from  the  air,  and  are  gradually  converted  into 
salts  of  sesquioxide  of  iron.  But  the  acid  present  is 
not  sufficient  to  dissolve  all  the  oxide,  as  this  has  a 
greater  capacity  for  saturation,  that  is,  requires  more 
acid  for  its  solution  than  the  protoxide  of  iron  does ; 
therefore,  a  portion  of  the  oxide  formed  falls  to  the  bot- 
tom. For  the  same  reason,  a  sesquioxide  or  peroxide  al- 
ways separates  from  the  protoxide  salts  of  the  other  met- 
als, when  they  are  converted  into  higher  oxide  salts.  A 
clear  solution  may  be  obtained,  by  adding  a  sufficient 
quantity  of  acid  to  dissolve  the  precipitated  oxide. 

Experiment  b.  —  Boil  half  an  ounce  of  green  vitriol 


328 


HEAVY     METALS. 


with  an  ounce  and  a  half  of  water  and  one  dram  of 
sulphuric  acid,  in  a  porcelain  bowl,  and  add  a  few  drops 
of  nitric  acid  to  the  solution,  until  the  color  of  it  is 
changed  to  yellow;  it  now  contains  sulphate  of  sesqui- 
oxide  of  iron  in  solution,  which  must  be  kept  for  use. 
The  same  effect,  namely,  the  conversion  of  the  protox- 
ide into  sesquioxide  of  iron,  is  thus  quickly  produced 
by  the  oxygen  of  the  nitric  acid,  which  in  the  former 
experiment  was  only  slowly  caused  by  the  action  of  the 
air.  Three  atoms  of  oxygen  are  withdrawn  from  the 
nitric  acid,  and,  accordingly,  nitric  oxide  is  produced 
(§  162),  which  has  the  property  of  imparting  to  a  solu- 
tion of  green  vitriol  a  dark  color.  On  boiling,  the  nitric 
oxide  escapes,  and  is  converted  in  the  air  into  nitrous 
acid,  forming  the  yellow  fumes  that  are  given  off  dur- 
ing the  oxidation. 

Experiment  c.  —  Prepare  (1.)  a  diluted  solution  of 
green  vitriol,  (2.)  a  mixture  of  one  part  of  a  solution  of 
sulphate  of  sesquioxide  of  iron  and  four  parts  of  water 
(see  former  experiment),  and  (3.)  a  mixture  of  the  first 
and  second ;  and  then  add  ammonia  to  each  of  the 
three  liquids,  until  they  emit  a  distinct  ammoniacal 
odor.  There  is  formed  in  the 

1.  Solution  of  protoxide  of  iron,  a  greenish  white  pre- 
cipitate of  hydrated  protoxide  of  iron  ; 

2.  Solution  of  magnetic  oxide  of  iron,  a  black  precip 
itate  of  hydrated  magnetic  oxide  of  iron ; 

3.  Solution  of  sesquioxide  of  iron,  a  yellowish  brown 
precipitate  of  hydrated  sesquioxide  of  iron. 

Ammonia  is  a  stronger  base  than  either  protoxide  or 
sesquioxide  of  iron ;  for  this  reason,  it  abstracts  from 
them  their  sulphuric  acid,  and  the  oxides  will  be  precip- 
itated, since  almost  all  the  metallic  oxides  are  insoluble 
in  water.  If  the  metallic  oxides,  at  the  moment  of  their 


IRON. 


329 


Soluble. 


insoluble. 


separation    from    a    combination,   meet    with    water, 

they   readily  com- 
bine with  it,  form- 
ing hydrates.    This 
is  the  reason  why 
the  metallic  oxides, 
insoluble,     which  are  obtained 
in  the  moist  way, 
frequently  have  a  very  different  color  from  those  prepared 

in  the  dry  way  (by 
Soluble.  .  heating  to  redness). 
If  you  heat  the 
hydrate,  the  water 
is  expelled,  and  the 
oxides  appear  now 
in  their  character- 
istic color.  This  change  of  color  is  well  illustrated  in 
the  case  of  common  bricks,  which,  before  being  burnt, 
have  a  yellow  color,  owing  to  the  presence  of  hydrated 
sesquioxide  of  iron ;  when  burnt,  they  are  red,  because 
the  hydrated  water  is  expelled  by  the  heat,  and  thereby 
anhydrous  sesquioxide  of  iron  is  formed,  which  pos- 
sesses a  red  color.  If  the  above  precipitates  are  filtered, 
a  striking  change  is  soon  perceptible  in  the  protoxide 
of  iron,  its  color  changing  first  to  a  dark  green,  then  to 
black  (magnetic  oxide  of  iron),  and  finally  to  brown 
(hydrated  sesquioxide  of  iron),  according  to  the  amount 
of  oxygen  absorbed.  As  already  stated,  one  of  the  most 
important  properties  of  protoxide  of  iron  is,  that  it 
combines  eagerly  with  still  more  oxygen,  a  property 
which,  as  we  have  seen,  it  communicates  also  to  the 
salts  in  which  it  is  contained. 

The  black  precipitate  of  magnetic  oxide  of  iron  com- 
ports itself  in  the  same  manner.     But  if  you  boil  it  pre- 
28*  _ 


330 


HEAVY     METALS. 


viously  to  filtration,  it  will  retain  its  black  color  on  dry- 
ing. In  this  state  it  is  used  as  a  medicine,  under  the 
name  of  black  oxide  of  iron. 

Experiment  d.  —  If  you  pour  alcohol  upon  some 
bruised  nutgalls,  the  liquor,  after  a  few  days,  will  have 
a  brownish-yellow  color,  and  a  very  astringent  taste. 
This  liquid  —  called  tincture  of  galls  —  contains  in  so- 
lution, besides  several  other  ingredients,  two  organic 
acids,  tannic  acid,  or  tannin,  and  gallic  acid.  Add 
some  of  this  tincture  to  a  solution  of  green  vitriol,  and 
some  of  it  likewise  to  a  mixture  of  water  and  sulphate 
of  sesquioxide  of  iron ;  in  the  former,  a  light-colored  pre- 
cipitate will  be  formed,  which  assumes  at  first  a  violet^ 
and  finally  a  black  color ;  but  in  the  second  liquid  a 
black  color  is  immediately  produced ;  and,  on  standing,  a 
black  precipitate  will  be  deposited.  This  black  precip- 
itate consists  principally  of  tannate  and  g-allate  of  sesqui- 
oxide of  iron.  By  adding  to  this  gum  or  sugar,  com- 
mon ink  is  prepared,  the  mucilaginous  or  saccharine 
liquid  thus  obtained  holding  the  gallate  and  tannate  of 
iron  in  suspension.  The  combination  of  tannin  and 
gallic  acid  with  protoxide  of  iron  is  not  black,  but  it 
becomes  so  on  exposure  to  the  air,  since  the  protoxide 
is  thus  converted  into  sesquioxide.  This  explains  the 
pale  color  of  fresh  ink,  and  its  becoming  dark  on  the 
paper.  If  you  dip  a  linen  rag  first  in  tincture  of  galls, 
and  then  in  a  solution  of  iron,  the  black  precipitate  is 
formed  in  the  fibre  itself,  and  thus  adheres  so  firmly  to 
it  that  it  cannot  be  washed  out  again.  This  is  the 
general  method  used  for  dyeing  cloth,  leather,  hair,  &c., 
either  black  or  gray,  and  for  this  reason  the  iron  salts, 
especially  green  vitriol,  have  a  very  extensive  applica- 
tion in  dyeing  and  calico-printing. 

286.  Nitrate  of  sesquioxide  of  iron  (Fe2  O3, 3  N  O6)  is 


IRON.  331 

obtained  by  adding  iron  filings  to  diluted  aquafortis,  aa 
long  as  they  continue  to  dissolve  in  it.  Nitric  acid  fur- 
nishes an  abundant  supply  of  oxygen  to  the  iron,  and 
this  takes  up  as  much  oxygen  as  it  can  bind,  and  is 
converted  into  a  sesquioxide.  This  solution  is  of  a 
brown  color,  and* is  used  in  dyeing.  If  some  aquafortis 
is  dropped  upon  cast-iron,  steel,  or  bar-iron,  black  spots 
are  produced,  because  the  iron,  but  not  the  carbon,  is 
dissolved.  These  spots  are  darker  in  cast-iron,  and 
lighter  in  bar-iron.  Hence,  to  ascertain  how  much  car- 
bon is  contained  in  a  sample  of  iron,  you  have  only  to 
dissolve  a  weighed  quantity  of  it  in  diluted  nitric  acid, 
and  to  weigh  the  charcoal  remaining  behind. 

287.  Acetate  of  sesquioxide  of  iron  may  be  prepared 
directly,  by  dissolving  freshly  precipitated  and  still  moist 
hydrated   sesquioxide  of  iron   in   acetic  acid.     When 
mixed  with  alcohol  and  ether,  it  forms  Klaprottts  ethe- 
real tincture  of  acetate  of  iron,  which  is  sometimes  used 
as  a  medicine.     When  the  shoemaker  pours  beer  upon 
iron  nails  to  prepare  the  iron-black  with  which  he  black- 
ens his  leather,  he  obtains  acetate  of  sesquioxide  of  iron; 
for  on  exposure  to  the  air  the  beer  is  changed  into  vin- 
egar, and  the  iron  to  sesquioxide.     Leather  is  a  combi- 
nation of  the  skin  with  tannin  ;  when  the  latter  meets 
with  the  sesquioxide  of  iron,  black  tannate  of  iron  (ink) 
is  formed.     An  iron  mordant  is  now  frequently  pre- 
pared for  dyeing  purposes,   by  dissolving  iron-rust  in 
wood-vinegar  (pyrolignite  of  iron). 

288.  Phosphate  of  protoxide  of  iron  is  prepared  by 
mixing  a  solution  of  green  vitriol  with  a  solution  of 
phosphate  of  soda ;  the  white  precipitate  produced  be- 
comes gradually  blue  by  attracting  oxygen  from  the  air 
(phosphate  of  the  magnetic  oxide  of  iron,  blue  iron- 
earth).     Phosphate  of  sesquioxide  of  iron  is  white,  ana 
occurs  in  the  ashes  of  many  plants. 


332  HEAVY    METALS. 

Iron  and  Oilorine. 

289.  Protochloride  of  Iron  (Fe  Cl),  a  green  salt,  is 

formed     by     dissolving 
Volatile,     iron   in   muriatic    acid ; 
sesquichloride     of    iron 
Non-       (Fe2  C13),  a  brown  salt, 

volatile.        *          ,.         ,    . 

by  dissolving  sesqmox- 
ide  of  iron  or  hydrated  sesquioxide  of  iron  in  muriatic 
acid,  or  by  the  addition  of  chlorine  water  to  protochlo- 
ride  of  iron  (§  186).  Protochloride  of  iron  is  also  called 
muriate  of  protoxide  of  iron,  and  sesquichloride  of  iron 
is  often  called  muriate  of  sesquioxide  of  iron. 

Iron  and  Cyanogen. 

As  chlorine  combines  with  iron,  so  also  cyanogen 
can  form  combinations  with  iron.  Two  of  them,  Prus- 
sian blue  and  yellow  prussiate  of  potassa,  have  acquired 
very  great  importance  in  the  arts. 

290.  Prussian  Blue,  or  Ferrocyanide  of  Iron 
(3  Fe  Cy  +  2  Fe2  Cy3). 

If  magnetic  oxide  of  iron  is  agitated  with  prussic 
acid,  the  black  precipitate  becomes  blue ;  this  insoluble 
compound  is  termed  Paris  blue;  or,  when  it  is  mixed 
with  white  substances,  —  for  instance,  alumina,  clay, 
starch,  &c.,  —  Prussian  or  mineral  blue.  Its  constitution 
may  be  more  readily  imprinted  on  the  memory  by  re- 
garding it  as  prussiate  of  black  oxide  of  iron.  It  con- 
sists, in  fact,  of  protocyanide  and  sesquicyanide  of  iron, 
since  a  haloid  salt  and  water  are  always  formed  when  a 
hydrogen  acid  combines  with  a  metallic  oxide  (§  187). 
Both  modes  of  consideration  harmonize  well  with  each 
other,  for  prussiate  of  protoxide  of  iron  is  the  same  as 
cyanide  of  iron  +  water, 


IRON.  333 

Fe  O  +  H  Cy  =  Fe  Cy  +  HO; 

and  prussiate  of  sesquioxide  of  iron   is   the  same  as 
sesquicyanide  of  iron  -f-  water, 

Fe2  O3  +  3  HCy  =  Fe,  Cy3  +  3  H  O. 

Prussian  blue,  on  account  of  its  splendid  color,  is  not 
only  an  important  article  for  staining  wood,  paper,  &c., 
but  it  is  also  one  of  the  principal  pigments  for  dyeing 
cloth,  cotton,  silk,  &c.  The  color  thus  prepared  is 
called,  in  dyeing  establishments,  potassa  blue^  to  distin- 
guish it  from  indigo  blue.  Prussian  blue,  although  it 
contains  prussic  acid  or  cyanogen,  is  not  poisonous. 
Similar  inconsistencies  frequently  occur  in  chemical 
combinations.  Sometimes  a  poisonous  combination  is 
formed  from  innocuous  bodies ;  and  sometimes  a  harm- 
less compound  from  poisonous  constituents.  Accord- 
ingly, a  correct  inference  cannot  always  be  drawn  as  to 
the  medical  effects  of  a  compound  merely  from-  its  con- 
stituents. 

Experiment.  —  Mix  thoroughly  together  one  dram  of 
Paris  blue  (pure  Prussian  blue)  and  a  quarter  of  a  dram 
of  oxalic  acid,  with  some  water;  the  color  insoluble 
in  water  is  rendered  soluble  by  the  oxalic  acid,  and  a 
blue  liquid  is  obtained,  which,  if  thickened  with  gum 
Arabic,  may  be  used  as  a  blue  ink. 

Experiment.  —  If  you  heat  some  Prussian  blue  upon 
charcoal  before  the  blow-pipe,  an  empyreumatic  odor  is 
produced;  the  cyanogen  is  consumed  (C2  N  is  con- 
verted by  the  oxygen  of  the  air  into  2  C  O.^  and  N),  and 
you  finally  obtain  only  a  brownish-red  residue  of  ses- 
quioxide of  iron.  Most  of  the  cyanogen  compounds 
are  decompcfsed  in  a  similar  manner  by  being  heated 
to  redness. 


334 


HEAVY    METALS. 


291.  Ferrocyanide  of  Potassium^  or  Prussiate  of  Potassa 

(2KCy,  FeCy  +  3  HO). 

Experiment.  —  Heat  to   boiling  an  ounce  of  finely 
pulverized  Prussian  blue  with  three  ounces  of  water, 
and  as  it  boils  add  gradually  caustic  potassa,  until  the 
bin 3  color  of  the  mixture  disappears.     You  obtain  a 
turbid,  brownish-yellow  liquid,  which  you  render  clear 
by  nitration.     What  remains  upon  the  filter  is  hydrat- 
ed    sesquioxide    of    iron,    which   is    separated    by   the 
stronger   potassa   from   the    Prussian    blue.      Tabular 
crystals  are  deposited,  on  cooling,  from 
the   clear   yellowish   liquid;    they   are 
commonly   called   yellow   prussiate  of 
potassa,  but  in  chemical  language  fer- 
rocyanide  of  potassium.     This   double 
salt  is  formed  as  follows :  — 

Prussian  blue :  iron  with  more  cyanogen  -}-  iron  with  less  cyanogen, 
Potassa :  oxygen  and  potassium, 

Water :  water, 

C  cyanide  of  potassium  -J-  pro- 
Products .          hydrated  sesquioxide  of  iron,  J     tocyanide  of  iron> 

(Insoluble.)  (Soluble.) 

The  potassium  of  the  potassa,  as  we  see,  replaces  the 
iron  in  the  sesquicyanide  of  iron,  forming  cyanide  of  po- 
tassium, which  forms  a  double  salt  with  the  remaining 
undecomposed  protocyanide  of  iron.  The  oxygen  of 
the  potassa  passes  to  the  liberated  iron,  and  converts  it 
into  sesquioxide  of  iron.  Accordingly,  we  have  in  the 
yellow  salt  potassium  and  iron  both  combined  with 
cyanogen.  As  water  is  present,  the  cyanide  of  potas- 
sium may  be  regarded  also  as  prussiate  of  potassa,  and 
the  protocyanide  of  iron  as  the  prussiate  of  protoxide  of 
iron,  and  the  whole  salt  as  a  combination  of  potassa 
and  protoxide  of  iron  with  prussic  acid.  Such  being 


IRON.  335 

the  case,  the  prassic  acid  may  be  expelled  from  it  by  a 
stronger  acid ;  this,  in  fact,  does  take  place,  for  prussic 
acid  is  commonly  prepared  from  this  salt  by  adding  to 
it  sulphuric  or  phosphoric  acid  and  some  water,  and 
then  distilling  the  mixture. 

If  blood  and^potassa  lye  are  boiled  together  and 
evaporated  to  dryness,  and  the  remaining  mass  is 
heated  to  redness,  a  yellow  solution  of  ferrocyanide  of 
potassium  is  obtained  by  the  lixiviation  of  it  with  water. 
This  salt,  prussiate  of  potassa,  must  not  be  confounded 
with  cyanide  of  potassium,  a  combination  consisting 
of  potassium  and  cyanogen  alone,  without  iron,  and 
which  is  a  white  salt  and  a  most  deadly  poison.  The 
ferrocyanide  of  potassium  (the  use  of  which  term  instead 
of  prussiate  of  potassa  will  prevent  the  liability  of  mis- 
taking one  compound  for  the  other)  is  not  poisonous. 

Ferrocyanide  of  potassium  is  prepared  on  a  large 
scale  in  a  manner  similar  to  that  above  described. 
Blood,  horn"  leather,  or  other  animal  substances,  are 
charred ;  this  is  best  done  by  dry  distillation,  in  order 
to  obtain  ammonia  as  a  secondary  product  (§  228) ;  the 
charcoal  thus  obtained  is  then  mixed  with  carbonate  of 
potassa  and  iron,  and  the  mixture  fused  at  a  red  heat 
in  a  reverberatory  furnace.  In  animal  charcoal  there  is 
still  contained  nitrogen.  This  nitrogen,  when  heated  to 
redness  with  a  strong  base,  unites  with  carbon,  forming 
cyanogen.  The  cyanogen  then  enters  into  combination 
with  the  potassium  of  the  carbonate  of  potassa,  which 
is  reduced  by  means  of  the  coal,  forming  cyanide  of 
potassium.  By  dissolving  the  fused  mass  in  water,  a 
portion  of  the  salt  gives  up  its  cyanogen  to  the  iron, 
whereby  ferrocyanide  of  potassium  (and  caustic  po- 
tassa) is  formed,  which,  after  sufficient  evaporation, 
crystallizes  from  the  solution.  More  recently  the  nitro- 
gen of  the  air  has  been  successfully  used  for  the  forma- 


336 


HEAVY    METALS. 


tion  of  cyanogen,  whereby  animal  substances  have 
oecome  quite  superfluous  in  the  preparation  of  ferrocy- 
anide  of  potassium. 

292.  Experiments  with  Ferrocyanide  of  Potassium. 

Experiment  a.  —  By  mixing  a  solution  of  ferrocy- 
anide  of  potassium  with  sulphate  of  sesquioxide  of  iron 
a  deep  blue  precipitate  of  Prussian  blue  is  produced; 
for  from 

Ferrocyanide  of  potassium :  protocyanide  of  iron  -\-  cyanide  of  potassium,  and 
Sulphate  of  sesquioxide  of  iron :  -  iron,  oxygen,  and  sulphuric  acid, 

f         ,  C  protocyanide  of  iron  -f-  sesquicyanide  of  iron 
ea  i  (insoluble),  and  sulphate  of  potassa  (soluble). 

Experiment  b.  —  Mix  a  solution  of  ferrocyanide  ol 
potassium  with  a  solution  of  green  vitriol ;  a  light  blue 
precipitate  is  formed  (prussiate  of  protoxide  of  iron  and 
potassa,  or  ferrocyanide  of  iron  and  potassium).  Set 
aside  one  half  of  the  solution,  frequently  stirring  it ;  the 
light  color  of  the  precipitate  gradually  changes  to  a 
darker  blue.  This  change  takes  place  more  rapidly  by 
adding  to  the  other  portion  a  few  drops  of  nitric  acid, 
and  heating  the  mixture.  In  both  cases  oxidation 
takes  place,  whereby  a  portion  of  the  protoxide  is  con- 
verted into  the  oxide,  so  that  prussiate  of  the  magnetic 
oxide  of  iron  or  ferrocyanide  of  iron  is  formed.  Both, of 
the  methods  here  given  are  employed  in  the  preparation 
of  Prussian  blue  on  a  large  scale.  In  dyeing,  the  cloth 
is  first  steeped  in  a  solution  of  iron,  and  then  passed 
through  a  slightly  acidified  solution  of  ferrocyanide  of 
potassium. 

Experiment  c.  —  Add  a  solution  of  ferrocyanide  of 
potassium  to  a  very  diluted  solution  of  blue  vitriol; 
you  obtain  a  purple  red  precipitate  of  ferrocyanide  of 
copper.  The  copper  gives  up  its  oxygen  and  sulphuric 
acid  to  the  potassium  of  the  ferrocyanide  of  potassium, 


IRON.  337 

and  sulphate  of  potassa  remains  dissolved  in  the  liquid. 
This  is  the  most  accurate  test  for  detecting  the  presence 
of  copper  in  a  liquid.  Most  of  the  basic  elements,  like 
copper  in  this  instance,  form  double  compounds  with 
protocyanide  of  iron. 

Experimented.  —  Sprinkle  some  ferrocyanide  of  po- 
tassium upon  a  piece  of  red-hot  sheet-iron,  and  quench 
it  quickly  in  cold  water;  the  iron  becomes  so  hard  as 
to  resist  the  action  of  the  file,  a  coating  of  steel  having 
been  formed  on  its  surface  by  the  carbon  of  the  cyano- 
gen. This  simple  process  is  especially  adapted  for  im- 
parting to  agricultural  implements  a  greater  degree  of 
hardness  and  durability. 

293.  Red  prussiate  of  potassa,  or  ferricyanide  of  po- 
tassium^ is  distinguished  from  the  yellow  prussiate  by 
containing   sesquicyanide   instead   of  protocyanide  of 
iron.     When  added  to  salts  of  the  protoxide  of  iron  it 
forms  a  deep  blue  precipitate  (but  no  precipitate  is  pro- 
duced by  it  in  the  salts  of  the  sesquioxide  of  iron)  ; 
therefore,  it  is  not  only  used  for  producing  a  blue  color, 
but  also  as  a  reagent  to  distinguish  the  salts  of  the 
sesquioxide  from  those  of  the  protoxide  of  iron. 

Iron  and  Sulphur. 

294.  Experiment. —  Protosulphuret  of  Iron  (Fe  S).  — 
On  adding  soi  le   sulphuretted   hydrogen  water  to   a 
slight!)  acidified  -olution  of  green  vitriol,  no  precipitate 
is  produce1 :  but  if  sulphuret  of  ammonium  is  added, 
a  deep  blacJ«   precipitate  is  formed ;  this  precipitate  is 
sulphuret  of  irnn 

295.  Experiment,  —  Sesquisulphuret  of  Iron.  —  Twen- 
ty grains  of  sulphur  and  thirty  grains  of  iron  filings  are 
thoroughly   mixed    and   heated   before   the    blow-pipe 
flame  directed  upon  one  part  of  the  mass ;  this  part  al- 

29 


338  HEAVY    METALS. 

tains  a  reel  heat,  which  rapidly  pervades  the  whole  mass. 
The  yellowish-brown  substance  obtained  is  sesquisul- 
phuret  of  iron.  Another  method  of  preparing  this  sub- 
stance, and  of  applying  it  to  the  evolution  of  sulphuret- 
ted hydrogen,  has  been  described  (§  131).  This  com- 
bination  also  occurs  native  (magnetic  pyrites).* 

Experiment.  —  If  you  moisten  protosulphuret  of  iron 
with  water,  and  let  it  remain  exposed  to  the  air  foi 
some  weeks,  small  green  crystals  will  be  found  dissem 
iriated  throughout  the  mass,  both  the  iron  and  the  sul- 
phur having  gradually  attracted  oxygen  from  the  air. 
Fe  S  is  thus  converted  into  Fe  O,  SO,. 

296.    Bisulphuret  of  Iron  (Fe  S2).  —  Iron  containing 
twice  as  much  sulphur  as  the  protosulphuret  occurs 
native  in  many  ores,  and  frequently  in  hard  coal,  and  is 
called  iron  pyrites  or  bisulphuret  of  iron.     It  has  quite 
Fig.  143.        the  appearance  of  brass,  and  usually  oc- 
curs in  cubic  crystals.     If  heated  in  a  re- 
tort, half  of  the  sulphur  distils  over,  and  is 
collected,  and  a  black   sulphuret  of  iron 
remains  behind ;  accordingly  sulphur  may 
be  prepared  from  it.      Green  vitriol  is  pre- 
pared from  this  residue,  by  piling  the  latter  in  heaps, 
and  leaving  it  for  several  months  exposed  to  the  air. 
The  green  vitriol  thus  formed  is  freed  from  earthy  im- 
purities by  lixiviation  and  evaporation. 

The  salts  of  iron  may  be  detected  by  their  behaviour 
before  the  blow-pipe,  by  ammonia,  tincture  of  galls, 
sulphuret  of  ammonium,  and  ferrocyanide  of  potas- 
sium. 


*  The  composition  of  magnetic  pyrites  generally  corresponds  to  the 
formula  Fe?  Ss  =  5  Fe  S  -j-  Fea  83.  —  Cours  Etimentaire  de  Chinue  pen 
RegnauU. 


MANGANESE.  339 

Systematic  Synopsis  of  the  Compounds  of  Iron. 

Iron. 

Carbnretted  Iron. 

a.)  Wrought-iron  (iron  -f-  \  per  cent,  of  carbon). 
b.)  Cast-iron  (iron  -f-  5  per  cent,  of  carbon) 
: }  Steel,  a. mixture  of  both. 

Sulphurets  ofilron. 
a.)  Sulphuret  of  iron,  black. 

6  )  Bisulphuret  of  iron,         yellow. 
c  )  Sesquisulphuret  of  iron,  brownish-yellow,  a  mixture  of  both. 

Oxides  of  Iron. 

a.)  Protoxide  of  iron,  black. 

Hydrated  protoxide  of  iron,     white. 
6  )  Sesquioxide  of  iron,  reddish-brown. 

Hydrated  sesquioxide  of  iron,  yellowish-brown. 
c.)  Magnetic  oxide  of  iron,  black. 

d.)  Ferric  acid  (lately  discovered). 

Salts  of  Iron. 
a.)  Stilts  of  the  Oxide. 

Salts  of  the  Protoxide.  Salts  of  the  Sesquioxide. 

(Green)  (Brown.) 

Sulphate  of  the  protoxide  of  iron.    Sulphate  of  the  sesquioxide  of  iron 
Nitrate  "  "  "  Nitrate  "  "  "  " 

Carbonate       " 

Acetate  "  "  «  Acetate          "      •    "  " 

Phosphate      "  "  "  Phosphate     "  "  " 

b).  Haloid  salts. 

Protochloride  of  iron.  Sesquichloride  of  iron. 

Ferrocyanide  of  potassium  (yellow).  Ferricyanide  of  potassium  (red). 
Ferrocyanide  of  copper  (red).  Ferrocyanide  of  iron  (blue). 


MANGANESE   (Mn). 
At.  Wt.  =  345  —  Sp.  Gr.  =  8. 

297.  Black  Oxide  or  Hyperoxide  of  Manganese 

(Mn  (X). 

Several  experiments  have  already  been  performed 
with  this  mineral,  which  is  chiefly  obtained  from  the 
Harz  Mountains  and  from  Thuringia ;  v  e  use  it  espe- 


340  HEAVY    METALS. 

cially  for  the  preparation  of  oxygen  and  chlorine*  J^  is 
one  of  the  few  combinations  of  oxygen  termed  ^per- 
oxides or  superoxides  ;  so  called  because  they  contain  an 
excess  of  oxygen,  which  they  give  out  when  heated  to 
redness,  or  when  heated  with  sulphuric  acid.  100 
ounces  of  black  oxide  of  manganese,  which  contain  36 
ounces  of  oxygen  (2  atoms),  yield  at  a  moderate  heat 
9  ounces  (-£-  atom),  at  an  intense  red  heat  12  ounces 
(|  atom^,  on  heating  with  sulphuric  acid  18  ounces 
(1  atom),  of  oxygen.  Therefore  hyperoxide  of  man- 
ganese is  excellently  adapted  for  combining'  other  bodies 
with  oxygen,  as  was  shown  in  the  preparation  of  chlorine, 
when  the  oxygen  of  the  hyperoxide  of  manganese  oxi- 
dized the  hydrogen  of  the  muriatic  acid,  forming  water, 
and  thereby  liberated  the  chlorine  of  the  muriatic  acid. 

Glass-makers  often  add  hyperoxide  of  manganese  to 
the  fused  glass,  to  render  the  color  of  the  black  or  dark- 
green  bottle-glass  yellow  or  orange,  a  shade  which  is 
generally  preferred.  In  this  case,  also,  an  oxidation  is 
effected  by  the  hyperoxide  of  manganese.  The  dark 
color  of  the  glass  is  owing  to  the  protoxide  of  iron ; 
this  obtains  oxygen  from  the  hyperoxide  of  manganese, 
and  becomes  sesquioxide  of  iron,  which  colors  the  fused 
glass  brown  or  yellow.  On  this  account,  black  oxide 
of  manganese  is  called  glass-makers'1  soap.  If  added  in 
small  proportions  to  white  glass,  it  gives  it  a  violet  color, 
and  in  this  way  artificial  amethysts  are  made. 

Experiment.  —  Mix  into  a  thin  paste  with  water  one 
fourth  of  a  dram  of  finely  pulverized  hyperoxide  of  man- 
ganese, one  dram  of  litharge,  one  of  clay,  and  spread 
it  over  a  tile.  Put  the  latter  between  two  glowing 
coals,  or  direct  upon  one  part  of  it  a  strong  blow-pipe 
flame;  the  mass  melts,  and  forms  on  cooling  a  brilliant 
black  coating,  or,  if  less  manganese  be  used,  a  brown 


MANGANESE. 


341 


coating.     This  is  the  method  by  which  potters  prepare 
their  black  or  brown  glaze. 

298.  Manganese   (Mn).  —  By  intensely   heating   the 
hyperoxide  of  manganese  with  charcoal,  all  its  oxygen 
may    be    expelled,    and    a   grayish-white   brittle   mass 
(Mn)  is  obtained,  much  more  difficult  of  fusion  than 
even  iron. 

Other  Combinations  of  Manganese. 

299.  Experiment.  —  Mix  in  a 'porcelain  crucible  a  quar- 

ter of  an  ounce  of  hyperoxide  of  man- 
ganese with  one  eighth  of  an  ounce 
of  sulphuric  acid,  and  expose  the 
mixture  to  a  gentle  heat  for  fifteen 
minutes,  and  then  to  a  strong  heat 
for  an  hour.  After  cooling,  boil  the 
black  mass  in  water,  and  evaporate 
the  solution  to  dryness,  constantly 
stirring  it  when  nearly  dry ;  the  reddish- white  powder 
is  sulphate  of  protoxide  of  manganese  (Mn  O,  SO3-[~ 
4  HO).  Half  of  the  oxygen  escaped  during  the  heat- 
ing, and  protoxide  of  manganese  (Mn  O)  remained  be- 
hind, which,  being  a  salt-base,  combined  with  the  sul- 
phuric acid.  Muriate  of  'protoxide  of  manganese,  or 
protochloride  of  manganese  (Mn  Cl),  was  formed  dur- 
ing the  preparation  of  chlorine  (§  150),  and  remained  in 
the  flask,  having  obtained  a  yellow  color  owing  to  the 
presence  of  chloride  of  iron.  Most  of  the  salts  of  the 
protoxide  of  manganese  have  a  reddish  color. 

300.  Dissolve  a  portion  of  the  sulphate  of  protoxide 
of  manganese,  and  use  the  solution  for  the  three  follow- 
ing experiments. 

Experiment  a. —  On  exposure  to  the  air,  the  solution 
acquires  a  dark-brown  color,  and  after  a  t^me  deposits 
29* 


342  HEAVY    METALS. 

a  powder  of  the  same  color,  just  a?  occurred  in  the 
solution  of  the  sulphate  of  protoxide  of  iron.  The 
protoxide  of  manganese  attracts  oxygen  from  the  air, 
and  is  converted  into  hydrated  sesquioxide  of  mauga- 
nese,  from  which  a  part  separates,  sufficient  acid  not 
being  present  to  retain  all  the  sesquioxide  in  solution. 

Experiment  b.  —  If  some  ammonia  or  potassa  is  added 
to  another  portion  of  the  solution,  the  stronger  bases 
will  overpower  the  sulphuric  acid,  and  hydrated  pro- 
toxide of  manganese  (MnO  -f-  HO)  will  separate  as  a 
white  precipitate.  On  filtering  and  drying,  it  will  be- 
come converted  into  dark-brown  hydrate  of  sesquioxide 
?f  manganese  (Mn^  O3  -f-  3  HO),  precisely  as  occurred 
with  the  hydrated  sesquioxide  of  iron.  If  a  piece  of 
linen,  immersed  in  the  solution,  is  dried,  and  then 
passed  through  a  solution  of  potassa,  the  precipitate 
will  adhere  firmly  to  the  fibres  of  the  cloth,  and  will  ac- 
quire, on  exposure  to  the  air,  a  fine  dark-brown  color, 
called  by  dyers  manganese-brown. 

Experiment  c.  —  Add  some  sulphuretted  hydrogen  to 
a  third  portion  of  the  solution  ;  no  change  takes  place 
until  some  ammonia  is  added,  when  a  flesh-colored  pre- 
cipitate is  produced,  consisting  of  manganese  and  sul- 
phur (Mn  S).  In  this  manner,  the  presence  of  manga- 
nese in  a  solution  may  be  ascertained,  for  manganese  is 
the  only  metal  which,  on  combining  with  sulphur, 
yields  a  metallic  sulphuret  of  a  pink  color.  This  ex- 
periment also  affords  another  example  of  double  elec- 
tive affinity  causing  a  decomposition  which  could  not 
be  effected  by  simple  elective  affinity. 

301.  Acids  of  Manganese.  —  Manganese  is  character- 
ized by  combining  with  still  more  oxygen  than  is 
already  contained  in  the  hyperoxide. 

Experiment. — Mix  intimately  together  in  a  mortal 


MANGANESE.  345 

one  dram  of  hyperoxide  of  manganese  and  one  dram 
of  caustic  potassa;  put  the  mixture  in  a  porcelain 
crucible,  and  heat  it  strongly  for  half  an  hour.  When 
coH;  add  some  water  to  the  black  mass;  you  will 
obtain  a  green  solution,  which  becomes  clear  by  set- 
tling in  a  te$t-tube.  This  green  color  is  owing  to 
the  formation  of  a  salt,  which  is  called  manganale  of 
potassa,  or  chameleon  mineral.  By  the  ignition  with 
potassa,  the  hyperoxide  of  manganese  is  disposed  lo 
receive  an  additional  atom  of  oxygen  from  the  air,  and 
Mn  CX  is  converted  into  Mn  O3,  which  latter  compound 
comports  itself  as  an  acid ;  that  is,  it  combines  with  the 
base  present,  forming  a  salt  (KO,  Mn  CX). 

Experiment.  —  Pour  half  of  the  green  solution  into  a 
wine-glass,  dilute  it  with  water,  and  leave  it  in  repose ; 
the  green  color  soon  begins  to  change,  passing  through 
bottle-green  and  violet  to  a  crimson-red,  a  brown  pow- 
der (hyperoxide  of  manganese)  being  at  the  same  time 
deposited.  This  apparently  voluntary  change  is  occa- 
sioned by  the  carbonic  acid  of  the  air,  which  combines 
with  a  portion  of  the  potassa  and  expels  the  manganic 
acid.  The  manganic  acid  (Mn  O3),  however,  on  being 
deprived  of  its  base,  immediately  separates  into  two 
parts,  one  of  which  contains  less  oxygen  (hyperoxide  of 
manganese,  Mn  (X),  and  the  other  more  oxygen  (per- 
manganic acid,  Mn,  O7)  ;  3  Mn  O3  is  converted  into 
Mn  O2  and  Mna  O7.  The  red  color  belongs  to  the  per- 
manganic acid,  which  remains  in  solution,  combined 
with  a  portion  of  the  potassa. 

Experiment.  —  Add  some  drops  of  sulphuric  acid  to 
another  portion  of  the  green  solution,  when  the  change 
of  color  from  green  to  red,  that  is,  the  conversion  of 
manganate  into  permanganate  of  potassa,  will  take 
place  instantaneously. 


344 


HEAVY     METALS. 


The  most  remarkable  characteristic  of  these  acids 
is  the  facility  with  ivhich  they  surrender  that  portion  of 
their  oxygen  which  stamps  them  as  acids.  Even  a 
piece  of  wood,  paper,  or  any  other  organic  substance, 
thrown  into  the  green  or  red  solutions,  decomposes 
them  and  removes  their  color,  and  for  this  reason  they 
should  never  be  filtered  through  paper.  From  its  sin- 
gular changes  of  color,  manganate  of  potassa  has  re- 
ceived the  name  of  chameleon  mineral. 

302.  Manganese  forms  with  oxygen  alone  a  great 
variety  of  combinations. 


345  Ibs.  of  manganese  form  with 

or  1  at.  Mn  "  " 

345  Ibs.  of  manganese  form  with 

or  1  at.  Mn  "  " 

345  Ibs.  of  manganese  form  with 

or  1  at.  Mn  "  " 

345  Ibs.  of  manganese  form  with 

or  1  at.  Mn  |  "  " 

345  Ibs.  of  manganese  form  with 

or  1  at.  Mn  "      " 


100  Ibs.  of  oxygen 

1  at.  O 
150  Ibs.  of  oxygen 

1  &  at.  O 
200  Ibs.  of  oxygen 

2  at.  0 

300  Ibs.  of  oxygen 

3  at.  O 

350  Ibs.  of  oxygen 
3k  at  O 


Protoxide  of   man- 
ganese, =  Mn  O. 
Sesquioxidc  of  man- 
ganese, =  Miig  Oa- 
Ilypcroxide  of  man- 
ganese, =  Mn  Oa. 
Manganic  acid, 

=  Mn  03. 

Permanganic  acid, 

=  Mn2  O7. 


It  is,  moreover,  hereby  rendered  very  obvious,  that  it 
is  the  quantity  of  the  oxygen  which  makes  one  and  the 
same  element  sometimes  a  base,  sometimes  an  acid. 
Some  idea  may  be  formed  of  the  great  army  of  salts 
which  manganese  alone,  in  virtue  of  this  double  char- 
acter, can  call  into  the  field,  when  we  reflect  that  it 
•not  only  combines  with  all  the  acids,  forming  protoxides 
and  sesquioxides,  but  also  with  all  the  bases,  forming 
manganates  and  permanganates. 


COBALT  (Co)  AND  NICKEL  (Ni). 
At.  Wt  =  368.  —  Sp.  Gr.  =  8.5.    At.  Wt.  =  369.  —  Sp.  Gr.  =  9. 

303.  Daring  the  Middle  Ages,  when  the  miner  held 
intercourse  with  earth-spirits  and  goblins  in  the  solitary 


COBALT    AND    NICKEL.  345 

depths  of  his  mines,  ores  were  occasionally  found,  par- 
ticularly in  the  mines  of  Schneeberg,  in  Saxony,  resem 
bling,  in  brilliancy  and  solidity,  the  finest  silver  ores, 
which,  however,  yielded  in  the  smelting  furnaces  no 
silver,  but  crumbled  away  to  a  gray  ashes,  a  disagree- 
able odor  of  garlic  being  at  the  same  time  emitted.  In 
accordance  with  the  superstitious  notions  of  those  times, 
the  miner  attributed  the  disappearance  of  the  supposed 
silver  to  the  malicious  jests  of  the  earth-spirits,  and 
contemptuously  rejected  these  ores,  which  he  baptized 
by  then*  names,  —  cobalt  and  nickel.  But  now  they  are 
held  in  high  estimation,  cobalt  being  used  for  impart- 
ing a  beautiful  blue  color  to  glass  and  porcelain,  and 
nickel  for  giving  to  brass  the  appearance  of  silver.  As 
these  metals  are  melted  only  with  great  difficulty,  the 
heat  of  the  old  furnaces  was  not  sufficient  to  fuse  them. 
The  odor  of  garlic  was  occasioned  by  the  arsenic,  which 
always  accompanies  the  ores  of  cobalt  and  nickel. 

304.  Smalt,  Azure,  or  Cobalt-blue.  —  The  ores  (white 
cobalt,  cobalt  pyrites,  cobalt  glance,  &c.)  containing 
arsenical  cobalt  and  nickel  are  now  worked  in  the  fol- 
lowing manner.  The  stamped  ores  are  first  roasted  in 
a  reverberatory  furnace,  to  expel  any  arsenic  that  may 
be  present,  and  to  convert  the  cobalt  into  oxide  of 
cobalt ;  then  it  is  mixed  with  sand  and  carbonate  of  po- 
tassa,  and  the  mixture  fused  in  clay  crucibles.  Thus  a 
glass  is  produced,  in  which  the  oxide  of  cobalt  dis- 
solves, imparting  to  it  a  deep  blue  color;  but  the  arseni- 
cal nickel,  together  with  some  silver  and  bismuth  pres- 
ent, collects  at  the  bottom  of  the  crucible  as  a  fused 
metallic  lump  (speiss).  The  melted  blue  glass  is  ren- 
dered brittle  and  friable  by  pouring  it  into  cold  water, 
after  which  it  is  ground  to  an  impalpable  powder,  and 
elutriated.  It  is  much  used,  under  the  name  of  smalt 


346 


HEAVY     METALS. 


and  azure,  not,  only  as  a  verifiable  pigment  for  glass, 
porcelain,  and  pottery,  but  for  coloring  paper,  and  also 
in  washing,  for  giving  a  blue  tint  to  linen  and  muslin. 

305  Wliite  Copper ',  or  German  Silver.  —  The  speiss, 
which  remains  after  the  fusion  of  the  cobalt  ore,  is  now 
generally  used  in  the  preparation  of  German  silver. 
The  arsenic  being  first  expelled,  the  bismuth,  silver,  and 
nickel  are  melted  with  from  four  to  five  times  as  much 
brass  (copper  and  zinc),  whereby  a  metallic  mixture  (an 
alloy)  of  a  silvery-white  color,  beautiful  brilliancy,  and 
great  malleability,  is  obtained.  This  alloy  is  extensively 
used,  as  a  substitute  for  silver,  in  the  manufacture  of  a 
great  variety  of  articles,  not  only  of  convenience,  but 
of  luxury. 

306.  As  pure  metals,  cobalt  and  nickel  have  a  great 
similarity  to    iron,  both  in  their    external    appearance 
and  in  their  combinations ;   but  they  are  nobler  met- 
als,   that   is,  they  do    not    attract   oxygen  with    such 
avidity,  and  they  do  not  rust  so  readily  as  iron.     The 
three  metals,  iron,  cobalt,  and  nickel,  constitute,  as  has 
been  already  mentioned,  the  magnetic  trio  ;  they  alone, 
of  all  the  metals,  are  attracted  by  the  magnet.     It  is, 
moreover,  remarkable,  that  just  these  three  metals  al- 
ways occur   in  meteorites,  which   occasionally  fall  to 
the  earth,  we  know  not   whence,  in  a   glowing  state 
(meteoric  iron,  meteoric  stones). 

The  fly-poison  of  the  apothecaries  is  also  frequently 
called  cobalt,  but  most  inappropriately,  as  it  does  not 
contain  a  particle  of  cobalt;  it  is  metallic  arsenic. 

307.  Both  these  metals,  like  iron,  form  with  oxygen 
a  protoxide  and  a  sesquioxide. 

Protoxide  of  cobalt  (Co  O)  is  of  an  ash-gray  color 
and  its  hydrate  is  pink;  sesquioxide  of  cobalt  (Co2  O3) 
is  black.  These  oxides  are  frequently  employed  in 
painting  on  porcelain  and  glass. 


ZINC.  347 

Protoxide  of  nickel  (Ni  O)  is  of  a  greenish-gray, 
and  its  hydrate  of  a  beautiful  apple-green  color ;  ses* 
quioxide  of  nickel  (Ni2  O3)  is  black.  Chrysoprase, 
known  as  an  ornamental  stone,  js  quartz,  colored  green 
by  protoxide  of  nickel. 

308.  The  $alts  of  protoxide  of  cobalt  are  of  a  pink 
color.     A  solution  of  the  nitrate  of  protoxide  of  cobalt  is 
often  used  in  blow-pipe  experiments,  especially  for  the 
detection   of  alumina  (§  262) ;  a  solution  of  protocJuo- 
ride  of  cobalt  is  employed  as  a  sympathetic  ink,  as  it 
possesses  the  property  of  becoming  blue  by  evaporat- 
ing  the   water,  and  again  pink    on  absorbing    water. 
Cobalt  forms,  with  phosphoric  and  arsenious  acids,  red 
insoluble  compounds,  which  are  now  employed  as  vit- 
rifiable  pigments  in  glass  and  porcelain  painting.     The 
salts  of  protoxide  of  nickel  have  a  light-green  color. 

The  salts  of  cobalt  and  nickel,  like  those  of  iron,  are 
not  precipitated  by  sulphuretted  hydrogen,  but  they 
are  by  sulphuret  of  ammonium,  as  black  sulphwret  of 
cobalt  and  nickel. 

•  ZINC  (Zn). 

At.  Wt.  =  407.  —  Sp.  Gr.=  6.8. 

309.  Not  very  long  ago,  zinc  was  hardly  used  except 
for  making  brass  and  pinchbeck ;  but  since  the   art  of 
rolling  it  out  into  plates,  of  forging  it,  and  of  drawing  it 
out  into  wire,  has  been  acquired,  it  is  used  also  for  the 
manufacture    of  many   articles    which   were   forr  .erly 
made  of  lead,  copper,  and  iron ;  for  instance,  for  making 
nails,  gasometers,  gas-pipes,  gutters,  and  for  covering 
roofs  of  houses,  for  lining  refrigerators,  &c.,  as  it  is  hard- 
er, and  yet  lighter,  than  lead,  cheaper  than  copper,  and 
less  liable  than  iron  to  be  destroyed  by  air  and  water, 


348  HEAVY     METALS. 

It  usually  occurs  in  commerce  in  the  form  of  sheets, 
which  are  so  brittle,  that  they  may  be  broken  by  the 
hammer  into  small  pieces  ;  the  fresh  fracture  exhibits  a 
hackly*  crystalline  structure,  and  a  bluish-white  color. 

310.  Experiments  with  Zinc. 

Experiment  a.  —  When  polished  zinc  remains  ex- 
posed to  the  air  for  some  time,  it  loses  its  lustre,  and  is 
covered  with  a  gray  film.  This  film  consists  of  zinc 
combined  with  a  small  quantity  of  oxygen,  and  is  called 
suboxide  of  zinc. 

Experiment  b.  —  If  a  piece  of  polished  sheet  zinc  be 
alternately  exposed  to  the  action  of  water  and  of  air,  it 
will  become  gradually  covered,  with  a  white  film ;  it 
rusts  like  iron,  but  the  rust  of  zinc  has  a  white  color. 
In  iron  the  oxidation  proceeds  rapidly  towards  the  inte- 
rior, but  not  in  zinc,  or  only  very  slowly;  therefore 
articles  made  of  zinc,  when  exposed  to  the  wind  and 
weather,  last  much  better  than  those  made  of  iron,  and 
for  this  reason,  also,  iron  articles  are  frequently  coated 
with  zinc  (galvanized  iron).  Iron-rust  is  hydrated  ses- 
quioxide  of  iron,  zinc-rust  is  hydrated  oxide  oP  zinc. 
Zinc  attracts  not  only  oxygen,  but  also  some  carbonic 
acid,  from  the  air,  and  this  may  be  recognized  by  the 
effervescence  which  follows  when  some  acid  is  dropped 
upon  the  rusted  zinc ;  consequently,  the  white  film  is  a 
double  compound  of  hydrated  oxide  of  zinc  with  car- 
bonate of  oxide  of  zinc  (basic  carbonate  of  the  hydrated 
oxide  of  zinc). 

Experiment  c.  —  Hold  a  piece  of  zinc  by  means  of  a 
pair  of  tongs  or  pincers  in  the  alcohol-flame,  until  it 
hisses  if  you  touch  it  with  a  piece  of  moist  wood ;  if 
you  now  quickly  hammer  it  upon  a  stone  or  anvil  pre- 

*  "  Hackly  fracture ;  when  the  elevations  are  sharp  or  jagged,  as  in  brok- 
in  iron."  —  Dana's  Manual  of  Mineralogy. 


ZINC. 


349 


viouely  heated,  it  does  not  break,  but  spreads  out  like 
lead  into  a  thin,  coherent  sheet.  Zinc  has  the  singular 
property  of  being  ductile  from  100°  C.  to  150°  C.,  but 
below  or  above  this  temperature  it  is  brittle.  Ever  since 
it  has  been  known  that  zinc  is  thus  affected  by  heat,  it 
has  been  foun^  easy  to  overcome  the  difficulties  which 
formerly  opposed  the  conversion  of  this  metal  (which 
is  unpliant  when  cold)  into  sheets  and  wire. 

Experiment  d.  —  Zinc,  when  heated  to  about  400°  C., 
melts,  as  may  easily  be  seen  by  holding  a  small  piece 
of  it  in  an  iron  spoon  over  an  alcohol  flame.  In  this 
case  a  gray  film  of  suboxide  is  likewise  formed ;  but 
this  after  a  time  assumes  a  yellow  color,  and  is  con- 
verted into  oxide  (Zn  O).  On  cooling,  the  yellow  color 
passes  to  white;  the  oxide  of  zinc  belongs  to  those 
substances  which  present  a  color  in  the  heat  different 
from  the  color  at  the  ordinary  temperature. 

Experiment  e.  —  In  chemical  experiments,  especially 
for  the  evolution  of  hydrogen,  it  is  very  convenient  to 
"use  zinc  in  the  form  of  small  grains  (granulated).  It 

is  very  easily  obtained 
in  this  state,  by  pour- 
ing the  melted  metal 
through  a  moistened 
broom,  gently  shaking 
it  while  it  is  held  over 
a  basin  of  water.  In 
this  way  the  other  ea- 
sily fusible  metals  al- 
so, such  as  lead,  tin, 
bismuth,  &c.,  may  be 
subdivided  into  smaller  parts,  and  with  much  more  fa- 
cility than  by  filing  or  cutting. 

Experiment  f.  —  At  a  still  stronger  heat,  zinc  evapo* 
30  •. 


350  HEAVY     METALS. 

rates ,  and  burns  at  the  same  time,  with  a  bluish  flame. 
In  this  experiment,  the  spoon  containing  the  zinc  must 
be  placed  on  red-hot  coals,  that  it  may  become  hotter 
than  by  the  spirit-lamp.  A  beautiful  appearance  is 
presented,  even  on  a  small  scale,  by  heating  a  piece  of 
zinc  upon  charcoal,  before  the  blow-pipe ;  the  metal  is 
soon  converted  into  a  loose,  spongy  mass  of  oxide,  and 
during  the  combustion,  blue  flames  burst  forth  from 
the  oxidized  coating.  The  oxide  is  not  volatile,  for  if 
it  were,  nothing  at  all  would  remain  behind.  The 
flame  is  caused  by  the  burning  fumes  of  zinc ;  the 
substance  formed  by  the  combustion  is  oxide  of  zinc. 
This  is  called  oxide  prepared  in  the  dry  way,  or  flowers 
of  zinc,  and  it  may  be  freed  from  any  admixture  of  me- 
tallic particles  by  elutriation.  Zinc  has  only  this  one 
degree  of  oxidation. 

Zinc  and  Acids. 

311.  All  diluted  acids  dissolve  zinc  with  ease,  with 
the  evolution  of  hydrogen,  and   form   with  the  oxide 
produced  salts  of  zinc.     The  hydrogen  liberated  in  this 
way  is  much  purer  than  that  prepared  with  iron ;  on 
this  account,  zinc  is  generally  employed  in  the  prepara- 
tion of  hydrogen,  namely,  for  Dobereiner's   hydrogen- 
lamp,  balloons,  &c.     If,  as  is  usually  done,  diluted  sul- 
phuric acid  is  taken  for  dissolving  the  zinc,  we  obtain 
on  evaporation  the  best  known  of  the  salts  of  zinc,  the 
sulphate  of  the  oxide  of  zinc. 

312.  Wldte  Vitriol,  or  Sulphate  of  Oxide  of  Zinc 

(ZnO,  SO3-+7HO). 

This  salt  crystallizes  in  colorless,  rhomboidal  prisms 
which  contain  nearly  half  their  weight  of  water  of  crys- 
tallization. Sulphate  of  the  oxide  of  zinc,  called  also 


ZINC. 


351 


white  vitriol,  is  easily  soluble  in  water,  and  is  often  em* 
ployed  as  a  cooling  application,  particularly  in  inflam- 
mation of  the  eyes.     Tolerably  large  quantities  of  thir. 
salt  may  be  prepared  without  much  trouble. 

Fig.  146.  AS  v        •  i       i    rx        r, 

by  evaporating   the  waste   liquids   leit   alter 


geuerating  hydrogen  from  zinc  and  sulphuric 
acid.  The  black  substance  which  deposits 
from  the  solution  of  zinc  is  for  the  most  part 
charcoal,  a  little  of  which  always  unites  with 
zinc  on  the  smelting  of  it  from  its  ores.  As 
it  is  not  soluble  in  acids,  it  must  remain  be- 
hind on  dissolving  the  metal. 
\  All  the  salts  of  zinc  are  poisonous,  and  ex- 

cite, when  introduced  into  the  stomach,  vio- 
lent vomiting ;  milk,  white  of  eggs,  and  coffee  are  em- 
ployed as  antidotes. 

Experiments  with  Wliite  Vitriol. 

a.)  Prepare  a  solution  of  white  vitriol,  and  add  to  it 
ammonia  or  potassa.  A  white  precipitate  of  hydrated 
oxide  of  zinc  is  formed,  which  dissolves  again  in  an 
excess  of  the  alkali. 

b.)  Sulphuret  of  ammonium ;  here  also  a  white  pre 
cipitate  is  produced ;  this  is  sulphuret  of  zinc.  This 
behaviour  of  zinc  is  taken  advantage  of  to  distinguish 
and  to  separate  it  from  other  metals.  Sulphuret  of 
zinc  also  occurs  native,  but  then  it  has  a  red  or  a 
brown  color,  and  is  called  zinc  blende.  From  this  ore, 
by  roasting,  weathering,  and  lixiviation,  white  vitriol  is 
prepared,  precisely  in  the  same  manner  as  green  vitriol 
is  obtained  from  sulphuret  of  iron. 

c.)  Carbonate  of  soda;  carbonate  of  the  hydratea 
oxide  of  zinc  is  obtained  likewise  in  the  form  cf  a 
white  precipitate.  If  this  is  dried,  after  having  b.cn 


352  HEAVY     METALS. 

previously  washed  with  water,  full  one  half  of  the  car- 
bonic acid  passes  off*;  when  heated  to  redness,  all  the 
carbonic  acid  and  the  oxide  of  zinc  remain  behind. 
The  oxide  thus  prepared  is  called  oxide  of  zinc  pre- 
pared in  the  moist  way. 

313.  Carbonate  of  zinc  occurs  also  in  nature  most 
abundantly,  in  Silesia,  Westphalia,  and  Belgium  ;  it  is 
the  most  important  zinc  ore,  and  from  it  the  metallic 
zinc  is  always  prepared  in  the  above-mentioned  places. 
The  miner  calls  this  ore  calamine,. 

314.  Preparation  of  Zinc.  —  In  order  to  convert  the 
calamine  into  metallic  zinc,  the  carbonic  acid  and  ox- 
ygen must  be   expelled.      The  first  is  effected  in   the 
same  way  as  with  carbonate  of  lime,  by  calcining  in 
furnaces,  and  the  latter  in  the  same  way  as  with  the 
iron  ores,  by  heating  to  redness  with  charcoal.     But  the 
process  of  reduction  cannot  be  conducted  in  open  fur- 
naces, for  in  them  the   reduced  zinc  would   evaporate 
and  burn  up  in  the  air,  forming  again  oxide  of  zinc, 
so  that  from  oxide  of  zinc  in  the  furnace  we  should 
only  obtain  oxide  of  zinc  in  the  air.     It  is  rather  a  pro- 
cess of  distillation  than  of  melting  that  we  must  under- 
take.    Clay  cylinders  or  muffles  are  employed  for  con- 
Fig.  147  ducting  the  distillation.      Several  ol 

these  are  ranged  in  circles,  or  are  piled 
one  above  the  other  in  a  furnace. 
The  annexed  figure  is  a  representa- 
tion of  a  muffle.  On  the  front  side 
of  it  is  a  projection  made  of  bent 
clay,  through  which  the  two  gaseous  substances,  car- 
bonic oxide  gas  and  zinc  fumes,  which  form  during 
the  heating  of  the  roasted  ore  and  charcoal,  may  escape. 
The  zinc  condenses  mostly  in  the  tube,  and  falls  down 
in  drops,  as  metal,  into  a  vessel^ontaining  water.  This 


CADMIUM. TIN. 


353 


is  again  to  be  melted  and  cast  into  sheets.  The  zin" 
of  commerce  always  contains  an  admixture  of  small 
quantities  of  iron  and  lead.  If  the  amount  of  lead  is 
more  than  one  and  a  half  per  cent.,  then  the  zinc  re- 
mains brittle,  even  when  heated,  and  cannot  be  rolled 
out  into  sheets. 

CADMIUM  (Cd). 
At.  Wt.  =  697.  —  Sp.  Gr.  =  8.6. 

315.  Cadmium  is  a  rare  metal,  and  may  be  regarded 
as  the  twin  brother  of  zinc,  in   the  ores  of  which  it  is 
found  in  small  quantities.     It  is  chiefly  distinguished 
from  zinc  by  its  malleability  when  cold,  and  by  being 
.precipitated  from  its  solution  by  sulphuretted  hydrogen 

as  yellow  sulphuret  of  cadmium.  As  already  mentioned, 
this  reagent  gives  no  precipitate  with  the  salts  of  zinc, 
but  the  latter  is  thrown  down  by  sulphuret  of  ammo- 
nium, as  white  sulphuret  of  zinc. 

TIN,   STANNUM  (Sn). 
At.  Wt.  =  756.  —  Sp  Gr.  =  7.2. 

316.  Tin  is  one  of  the  few  metals  which  were  known 
in  the  most  ancient  times.     It  becomes  fluid  at  a  very 
moderate  heat,   at  230°  C.,  and  in  many  countries  its 
ores  are  found  in  the  sand  withr  which  the  surf  ace  of  the 
soil  is  covered ;  therefore  it  was  easily  obtained  and 
easily  smelted.      Formerly  it    was  brought  principally 
from  the  British  Islands,  which  were,  therefore,  called 
also  Tin   Islands,  and  even  at  the  present  time  they, 
together  with   Malacca  in  the  East  Indies,  furnish  the 
purest  tin.     The  properties  which  especially  characterize 
tin,  and  render  it  a  very  valuable  metal,  are  its  beautiful 
lustre,  and  its  great  softness  and  flexibility,  —  its  slighi 

30* 


354  HEAVY     METALS. 

affinity  for  oxygen,  in  consequence  of  which  it  long 
retains  its  brightness  in  the  air  and  in  water,  —  its  easy 
fusibility,  which  renders  it  peculiarly  well  adapted  for 
casting,  and  for  coating  other  metals  (tinning').  It  has, 
indeed,  lost  much  of  its  earlier  importance  as  a  mate- 
rial for  making  many  vessels  of  domestic  u$e,  such  as 
dishes,  cans,  &c.,  since  such  articles  are  now  hand- 
somely and  cheaply  manufactured  from  glass  and  por- 
celain. But  it  is  now  applied  in  the  arts  and  trades 
in  a  variety  of  ways  not  formerly  in  use.  In  the  older 
works  on  chemistry,  it  is  called  Jupiter,  and  has  the 
symbol  }f. 

317.  Experiments  with  Tin. 

Experiment.  —  Heat  a  piece  of  tin  upon  charcoal  be- 
fore the  blow-pipe  ;  it  will  soon  become  covered  with  a 
powder,  of  a  yellow  color  when  hot,  but  white  when 
cold ;  this  is  peroxide  of  tin,  a  combination  of  one  atom 
of  tin  with  two  atoms  of  oxygen  (Sn  O2).  Peroxide  of 
tin  thus  obtained  is  not  soluble  in  any  acid,  and  cannot 
be  fused  by  the  strongest  heat.  It  is  so  delicate  a  pow- 
der, that  it  is  often  used  for  polishing  glass  and  metals. 

Tin  also  occurs  native  as  an  insoluble  oxide,  either 
crystallized  (crystals  of  tin  ore),  or  scattered  through  va- 
rious kinds  of  rocks  (tin-stone  of  Saxony  and  Bohemia), 
or,  finally,  as  an  ingredient  of  the  sand  or  debris  of  low 
grounds  in  many  countries  (wood-tin  in  England).  Ox- 
ide of  tin  is  the  only  ore  from  which  tin  is  largely  extract- 
ed ;  its  most  common  admixtures  are  iron  and  arsenic. 

Experiment.  —  Place  two  grains  of  tin  and  eight 
grains  of  lead  on  charcoal,  and  heat  them  before  the 
blow-pipe ;  they  melt  and  combine  most  intimately 
with  each  other ;  an  alloy  of  tin  and  lead  is  obtained 
If  this  is  heated  to  redness,  the  oxidation  proceeds  so 


TIN, 


355 


rapidly,  that  the  mass  takes  on  a  lively  motion,  and  con- 
tinues to  glow  even  when  it  is  removed  from  the  fire.    In 
this  manner  the  potter  prepares 
Fig.  148.  the  porcelain-like  glaze  for  earth- 

en baking-pans,  and  for  Delft 
ware.  Add  some  powdered  bo- 
rax to  this  mixture  of  oxides  of 
lead  and  tin,  and  form  with  it  a 
bead  upon  platinum  wire ;  the 
bead  is  not  transparent,  but,  ow- 
ing to  the  presence  of  the  infusi- 
ble peroxide  of  tin,  is  opaque,  and 
looks  like  porcelain  (enamel). 
318.  Alloys  of  tin  and  lead  are  generally  used  by 
workers  in  metal,  under  the  name  of  solder,  for  join- 
ing metals  together  (soft  soldering).  Solder  is  to 
the  tinman  what  glue  is  to  the  carpenter.  An  alloy  of 
two  parts  of  tin  and  one  part  of  lead  is  the  most  easily 
fusible,  arid  is  called  fine  solder.  Another  alloy,  used 
in  the  soldering  of  coarser  articles,  such  as  gutters,  is 
composed  of  two  parts  of  lead  and  one- part  of  tin,  and 
is  called  coarse  solder ;  it  is  so  thick  that  it  does  not 
spread  of  itself,  but  must  be  applied  by  smearing.  For 
soldering  those  metallic  articles  which  are  to  be  subject- 
ed to  a  stronger  heat,  brass,  or  some  other  alloy  of  diffi- 
cult fusibility,  is  made  use  of  (hard  solder  or  brazing-). 
Some  lead  is  added  even  to  the  tin  of  which  the  tin- 
man makes  his  articles,  because  pure  tin  is  somewhat 
brittle,  and  does  not  adapt  itself  well  to  the  moulds. 
The  quantity  of  lead  which  can  be  added  to  tin  is  fn 
many  countries  regulated  by  law  (|  to  I).  Such  an 
alloy  is  called  proof  tin,  to  distinguish  it  from  refined 
or  grain  tin,  which  is  tin  in  its  greatest  purity.  If  an 
acid,  such  as  i?  used  in  cookery,  be  poured  on  proof  tin 


356  HEAVY    METALS. 

.the  tin  only  is  dissolved;  tin  has,  accordingly,  the  powei 
of  protecting  lead  from  the  attacks  of  acids. 

*\: 

Tin  and  Muriatic  Acid. 

319.  The  most  important  solvent  of  tin  is  muriatic 
acid ;  the  two  most  important  salts  of  tin,  protochloride 
and  perchloride  of  tin,  are  prepared  by  means  of  it. 

Protochloride  of  Tin.  — Experiment.  —  Place  in  two 
^orcelain  bowls  or  earthen  pots  some  tinfoil,  and 
then  add  some  muriatic  acid  to  one  of  the  portions. 
After  some  hours  pour  this  acid  upon  the  tin  of  the 
second  vessel,  and  then  again  into  the  first  vessel,  re- 
peating the  process  so  that  the  metal  may  come  in 
contact  for  some  days  .  alternately  with  the  ah*  and  the 
muriatic  acid.  Protoxide  of  tin  is  formed  by  the  oxy- 
gen of  the  air ;  it  is  dissolved  by  the  acid.  We  thus 
obtain  a  solution  of  the  muriate  of  protoxide  of  tin,  or 
protochloride  of  tin,  from  which,  on  evaporation  and 
cooling,  colorless  rhomboidal  prisms  are  deposited.  In 
commerce  this  salt  is  called  salt  of  tin.  It  possesses,  in 
common  with  the  salts  of  protoxide  of  iron,  the  prop- 
erty of  attracting  with  great  avidity  still  more  oxygen 
from  the  air,  and  changing  into  a  peroxide  salt.  Thus 
is  explained  why  the  salt  of  tin,  which  has  been  for 
some  time  exposed  to  the  air,  no  longer  presents  a 
clear,  but  a  milky,  solution.  To  obtain  a  clear  solution, 
muriatic  acid  must  be  added,  which  combines  with  the 
precipitated  peroxide  of  tin. 

320.  Protoxide  of  Tin  (Sn  O).  —  Experiment.  —  Pour 
stfme  ammonia  upon  a  solution  of  salt  of  tin;  the 
white  precipitate  which  is  formed  is  hydrated  protoxide 
of  tin.  By  boiling  the  solution,  the  combination  of  the 
protoxide  and  water  is  destroyed,  and  an  anhydrous 
protoxide  of  tin  is  formed,  which  has  a  dark-green  col- 


TIN.  357 

or,  and  must  be  quickly  washed  with  boiled  water  and 
dried,  as  it  likewise  attracts  more  oxygen  from  the  air. 
If  you  heat  the  dried  protoxide  before  the  blow-pipe, 
it  burns  with  great  briskness,  like  tinder,  forming  per- 
oxide of  tin. 

321.  Perchloride   of   Tin   (Sn  C12). — Experiment. — 
Add  chlorine  water  to  a  solution  of  salt  of  tin,  until 
the  odor  of  chlorine  is  no   longer   destroyed.     Sn    Cl 
is  thereby  converted  into  Sn  C12,  or  perchloride  of  tin. 
This  combination  can  also  be  obtained  by  boiling  a 
solution  of  salt  of  tin  in  a  mixture  of  muriatic  acid  and 
nitric  acid,  or  by  dissolving  tin  in  aqua  regia.     The 
dyers  call  this  liquid  permuriate  of  tin,  tin  mordant,  or 
red  spirits.     By  the  addition  of  ammonia  peroxide  of 
tin  is  obtained,  which  is  distinguished  from  that  formed 
at  §  317  by  its  dissolving  very  easily  in  acids. 

Protoxide  and  peroxide jof  tin  dissolve  also  in  potassa 
lye,  and  comport  themselves,  like  alumina  (§  260),  as 
acids  towards  strong  bases. 

322.  Experiment.  —  If  a  few  drops  of  a  solution  of 
gold  are  added  to  a  very  diluted  solution  of  protochlo- 
ride  of  tin,  a  purple-red  precipitate  is  formed  (but  not  in 
a  solution  of  perchloride  of  tin),  which  is  called  purple 
of  Cassius,  or  gold  purple,  and  is  one  of  the  most  im- 
portant vitrifiable  pigments,  because  it  produces,  when 
fused  into  glass  or  porcelain,  the  most  superb  purple- 
red  color.     Solution  of  gold  is  a  good  test  for  the  salts 
of  the  protoxide  of  tin. 

323.  Experiment.  —  Mix  a  decoction  of  Brazil-wood 
with  protochloride  or  perchloride  of  tin;   the  yellowish- 
red  color  of  the  liquid  is  converted  into  a  beautiful  crim- 
son-red.     Similar  advantageous  changes  of  color  are 
also  effected  by  these  salts  in  other  coloring  matters, 
and  on  this  account  they  are  very  frequently  used  as 
so-called  mordants  in  dyeing  and  calico-printing. 


358  HEAVY    METALS. 

Tin  and  Nitric  Acid. 

324.  Experiment.  —  Heat  some   grains   of  tin  with 
nitric  acid  in  a  test-tube ;  the  tin  is  converted,  under  a 
brisk  evolution  of  yellow  fumes,  into  a  white  powder, 
peroxide  of  tin.     The  nitric  acid  will  perhaps  convert 
the  tin  into  an  oxide,  but  it  cannot  combine  with  the 
oxide   produced.     The  peroxide   of  tin  thus  obtained 
combines  indeed  with  other  acids,  but  not  so  completely 
as  that  obtained  according  to  f  321 ;  that  prepared  by 
heating  does  not  at  all  unite  with  them,  as  has  been 
already  stated  (§317).     Peroxide  of  tin  accordingly  oc- 
curs in  three  isomeric  states ;  namely  the  insoluble,  the 
very  easily  soluble,  and  the  difficultly  soluble,  in  acids. 

Tin  and  Sulphur. 

325.  Experiment.  —  Sulphuretted    hydrogen    water 
produces,  in  a  solution  of  protochloride  of  tin,  a  reddish- 
brown  precipitate  of  protosulphuret  of  tin  (Sn  S),  and 
in  a  solution  of  perchloride  of  tin  a  yellow  precipitate 
of  bisulphuret  of  tin  (Sn  S2).     It  is  obvious,  that  in  the 
first  case  one  atom  of  chlorine  is  replaced  by  one  atom 
of  sulphur,  and  in  the  latter  case  two  atoms  of  chlorine 
by  two  atoms  of  sulphur. 

Protosulphuret  of  Tin  (Sn  S).  —  Experiment.  —  Both 
these  metallic  sulphurets  may  be  prepared  in  the  dry 
way.  Envelop  12  grains  of  flowers  of  sulphur  in  a 
piece  of  tinfoil,  weighing  24  grains,  then  roll  up  the 
package  so  that  it  may  be  introduced  into  a  test-tube, 
and  heat  it ;  half  of  the  sulphur  burns  up,  but  the  other 
half,  under  a  lively  glowing,  combines  with  the  tin, 
forming  a  brownish-black  mass  of  a  metallic  lustre 
'Sn  S).  If  you  sprinkle  the  glass,  while  still  hot,  with 
water,  it  is  rendered  friable,  and  can  easily  be  separated 


TIN.  359 

from  the  fused  protosulphuret  of  tin.     The  weight  of 
the  latter  amounts  to  nearly  thirty  grains. 

BisulpJmret  of  Tin  (SnSJ. — ^Experiment. —  Pulver- 
ize the  thirty  grains  of  protosulphuret  of  tin  thus 
obtained,  and  mix  the  powder 
intimately  with  six  grains  of  sul- 
phur and  twelve  grains  of  sal 
ammoniac;  put  the  mixture  into 
a  thin -bottomed  glass  flask  of  an 
ounce  capacity,  and  heat  it  for  an 
hour  and  •  a  half  in  a  sand-bath. 
You  obtain  bisulphuret  of  tin,  but 
in  this  case  as  a  mass  having  a 
golden  lustre,  and  to  which  the 
name  aurum  musivum  or  mosaic  gold  has  been  given. 
It  may  be  used  for  giving  a  gold-like  coating  to  wood, 
gypsum,  clay,  &c.  (bronzing-).  The  sal  ammoniac  is 
found  again  as  a  sublimate  in  the  upper  portion  of 
the  flask ;  it  promotes  the  formation  of  the  beautiful 
gold  color,  without  itself  undergoing  or  producing  any 
chemical  change. 

326.  Preparation  of  Tin.  —  Tin  is  prepared  in  smelt- 
ing-houses,  in  a  very  simple  manner,  from  tin-stone 
(peroxide  of  tin).  The  finely  stamped  ore  is  first 
roasted,  by  which  process  the  arsenic  is  volatilized  and 
the  iron  oxidized.  Then  it  is  washed  or  elutriated 
with  water,  whereby  the  lighter  particles  of  stone  (the 
g-angue),  and  to  a  great  extent  also  the  oxide  of  iron,  are 
washed  away.  Finally,  it  is  fused  with  charcoal  in  a 
blowing-furnace,  and  carbonic  oxide  gas  and  metallic  tin 
are  obtained,  the  latter  of  which  flows  off  below.  The 
Saxony  tin  is  usually  cast  in  thin  sheets,  and  the  Eng- 
lish tin  in  slender  bars.  Most  of  the  tin  of  commerce 
contains  traces  of  arsenic  and  other  metals.  A  bar  of 


360  HEAVY    METALS. 

tin  emits  a  grating  sound  on  being  bent,  and  by  repeat 
ing  the  operation  several  times  in  succession,  it  becomes 
very  hot ;  the  reason  is,  that  the  tin,  on  hardening, 
assumes  a  crystalline  texture,  and  these  crystalline  par- 
ticles are  displaced  by  the  bending,  and  rub  against 
each  other.  These  crystals  may  be  very  beautifully  pro- 
duced upon  tinned-iron  sheets. 

Experiment.  —  Heat  a  piece  of  tin  plate  (tinned-iron 
plate)  upon  a  tripod,  over  a  spirit- 
lamp,  till  tKe  tin  is  melted;  then 
quench  it  with  water,  that  the  tin 
may  harden  quickly.     The  surface 
of  the  plate  has  a  dull  gray  aspect, 
for   it  is   covered   with   a   film    of 
oxide  ;  but  the  most  beautiful  crys- 
talline figures  will  very  soon  appear  upon  it  by  rubbing 
it  alternately  with  balls  of  paper,  one  of  which  is  mois- 
tened with  diluted  aqua  regia,  and  the  other  'with  po- 
tassa  lye.     Both   these  liquids  dissolve  the  coating  of 
oxide,  and  lay  bare  the  pure  metallic  tin  surface  (moiri 
metallique). 

327.  Tinning'.  —  Experiment.  —  The  method  of  coat 
ing  copper  or  brass  with  tin  has  already  been  described 
(§  229).  This  may  be  done  also  in  the  moist  way,  by 
heating  to  their  boiling  point  finely  divided  tinfoil,  or 
tin  scrapings,  in  a  pot  with  cream  of  tartar  and  water, 
and  then  boiling  for  half  an  hour  in  this  liquid  some 
brightly  polished  copper  or  brass  articles;  as,  for  in- 
stance, cents  or  brass  nails.  The  free  acid  of  the  cream 
of  tartar  effects  a  solution  of  some  of  the  tin,  and  on 
longer  boiling  this  tin  will  again  separate  as  a  metal 
upon  the  more  electro-positive  copper  or  brass,  as  in 
$  284.  In  this  manner  pins  are  tinned,  or  whitened. 
Experiment.  —  Let  some  vinegar  stand  over  night  in 


RETROSPECT.  361 

a  vessel  of  tin  plate,  and  then  test  it  with  a  solution  of 
gold ;  tne  purplish  color  which  forms  indicates  that 
even  the  weak  vinegar  can  dissolve  tin.  Tin  is  not  in- 
deed so  poisonous  as  lead  or  copper,  but  yet  it  is  in- 
jurious to  health  ;  therefore,  acid  food  and  drinks  should 
not  be  allowe^  to  stand  for  any  length  of  time  in  tin  or 
in  tinned  vessels. 

Spurious  silver-leaf  is  made  of  an  alloy  of  tin  and 
zinc,  which  is  hammered  out  into  extremely  thin 
leaves. 

URANIUM  (U> 
At.  Wt.  =  750.— Sp.  Gr.  =  ? 

328.  Uranium  is  one  of  the  rarer  metals,  and  occurs 
in  combination  with  oxygen  in  a.  black  mineral  called 
pitch-blende,  found  in  Saxony.  From  it  is  prepared 
the  uranate  of  ammonia,  a  beautiful  yellow  powder, 
known  in  commerce  under  the  name  of  oxide  of  ura- 
nium. At  a  white  heat  it  is  reduced  to  black  protoxide, 
and  yields  a  very  permanent  black  pigment  for  painting 
on  porcelain.  The  yellowish-green  (may-green)  glass, 
now  so  popular,  likewise  owes  its  color  to  the  oxide  of 
uranium. 

The  following  metals,  Cerium,  Lanthanium,  and  Di- 
dymium,  are  mentioned  here  only  by  name,  as  chemical 
rarities. 


RETROSPECT  OF  THE  FIRST  GROUP  OF  HEAVY 
METALS. 

1.  The  metals  hitherto  considered  possess  the  prop- 
erty of  decomposing  water,  when  they  are  heated  to 
redness,  or  with  the  presence  of  an  acid  (water-decom- 
31 


362  .          HEAVY    METALS. 

posing  metals)  ;  therefore  diluted  acids   are  employed 
for  dissolving  them. 

2.  At   their   lowest  degrees   of  oxidation,  they  are 
strong  bases. 

3.  None  of  these  metals  are  found  pure  in  nature; 
they   most   frequently   occur   as   oxides,   consequently 
combined  with  oxygen. 

4.  The  specific  gravity  of  these  metals  is  from  6.6 
to  8.8. 

5.  Iron,  manganese,  zinc,  cobalt,  and  nickel  are  not 
precipitated  as  sulphurets  from  their  acid  solutions  by 
sulphuretted  hydrogen,  but  only  by  sulphuret  of  ammo- 
nium (all  the  other  heavy  metals  are  converted  by  either 
of  the   solutions  into  sulphurets).     This  fact  is  made 
available    in    analytical    chemistry,    as    an   important 
means  of  separating  the  above-named  (electro-positive) 
from  the  other  (electro-negative)  metals. 


SECOND    GROUP    OF    HEAVY    METALS. 

LEAD,  PLUMBUM  (Pb). 
At.  Wt.=  1294.  — Sp.  Gr.  =  11.5. 

329.  Next  to  iron,  lead  is  the  most  widely  diffused 
and  the  cheapest  metal;  it  is,  at  the  same  time,  also 
very  useful,  not  merely  because  we  cast  shot  and  types 
from  it,  and  construct  sulphuric-acid  chambers  of  it, 
but  also  on  account  of  the  many  useful  combinations 
which  it  forms  with  oxygen  and  the  acids.  This 
metal  appears  as  an  enemy  to  human  health,  not, 
however,  openly,  but  under  the  mask  of  friendship : 
for  it  conceals  its  noxious  effects  behind  a  sweet  taste, 
which  is  peculiar  to  most  of  its  combinations.  These 
effects,  moreover,  do  not  manifest  themselves  immedi« 


LEAD.  363 

1 

ately  when  the  lead  enters  the  system  ;  it  is  often  only 
after  the  lapse  of  years  that  they  appear  (lead  colic) 
It  is,  for  this  reason,  classed  among  the  slow  poisons 
Perhaps,  also,  this  was  the  reason  why  it  was  formerly 
compared  with  the  god  of  time,  and  received  the  name 
of  Saturn  an4  the  sign  1^ . ;?  The  external  properties  of 
lead,  its  lustre,  its  easy  fusibility,  its  softness  and  pli- 
ability, its  high  specific  gravity,  &c.,  are  well  know^n ; 
therefore  we  shall  proceed  at  once  to  the  consideration 
of  its  internal  or  chemicaf  character. 

Experiments  ivith  Lead. 

330.  Experiment.  —  Pour  into  one  glass  distilled  wa- 
ter,  into   another   spring-water,    and   place   in  each  a 
piece  of  lead ;  the  distilled  water  soon  becomes  turbid, 
and  reacts  basically,  but  not  so  the  spring-water.     Pure 
water  readily   attacks   lead,   and   converts  it   into,  hy- 
drated  oxide  of  lead;  in  spring-water,  on  the  contrary, 
there  is  formed  in  time,  by  the  sulphates  almost  always 
present  in  it,  some   insoluble  sulphate  of  lead,  which 
forms  a  firm  coating  upon  the  metallic  lead.     This  ex- 
plains the   harmlessness  of  leaden   pumps,  which,  in 
many    countries,   are   quite  generally   used  instead   of 
wooden  pumps. 

331.  Experiment.  —  If  lead  is  heated  before  the  blow- 
pipe in  the  exterior  flame,  it  melts  at  about  32CP  C.,  and 
is  thereby  coated  with  a  gray  film  ;  indeed,  it  is  finally 
entirely  converted  into  a  gray  powder.     This  may  be 
regarded  either  as  suboxide  of  lead,  or  as  a  mixture  of 
oxide  of  lead  with  metallic  lead.     By  continued  blow- 
ing, this  gray  color  is  changed  to  yellow;  the  yellow 
body  is  protoxide  of  lead  (Pb  O).     At  a  stronger  heat 
the  oxide  melts,  and  solidifies  on  cooling  into  a  reddish- 
yellow  mass,  composed  of  brilliant   scales,   the   well 


304  HEAVY    METALS. 

known  litharge.  By  directing  upon  it  the  inner  blow- 
pipe flame,  metallic  lead  will  again  be  obtained.  This 
easy  reducibleness,  which  is  peculiar  to  almost  all  salts 
of  lead,  together  with  the  incrustation  of  yellow  oxide, 
deposited  upon  the  charcoal,  is  a  certain  test  for  the  pres- 
ence of  lead. 

Oxide  of  lead  contains,  for  every  100  pounds  of  lead, 
8  pounds  of  oxygen,  or  one  atom  of  lead  (1294)  and 
one  atom  of  oxygen  (100) ;  lead,  consequently,  is  one 
of  those  chemically  feeble  tfodies  which  have  a  very 
high  atomic  weight,  since  1295  pounds  of  it  is  able 
to  accomplish  only  as  much  as  350  pounds  of  iron, 
or  407  pounds  of  zinc.  Protoxide  of  lead  in  the  form 
of  litharge  has  a  very  great  application  in  the  arts  and 
trades.  How  lead-glass  (flint-glass),  lead-glaze,  and 
sugar  of  lead  are  prepared  from  it,  has  already  been  de- 
scribed ;  the  manufacturing  chemist  likewise  prepares 
from  it  red  lead,  white  lead,  and  other  lead  colors,  and 
lead  salts ;  the  apothecary  compounds  insoluble  soap 
(lead  plaster),  by  boiling  it  with  olive-oil ;  the  cabinet- 
maker makes  a  varnish  that  dries  rapidly,  by  boiling  it 
with  linseed  oil,  &c.  The  English  litharge  is  esteemed 
the  purest ;  that  of  Saxony  and  Goslar  always  contains 
small  quantities  of  oxides  of  copper  and  iron,  perhaps 
also  a  little  silver.  The  preparation  of  it  on  a  large 
scale  will  be  described  under  silver.  By  melting  li- 
tharge in  a  Hessian  crucible,  a  brownish-yellow  trans- 
parent glass  is  obtained  on  cooling ;  this  consists  of 
oxide  of  lead  combined  with  some  silicic  acid.  The 
silicic  acid  came  from  the  crucible. 

332.  Red  Oxide  of  Lead.  —  Experiment.  —  Heat  in 
a  ladle  one  dram  of  litharge  and  a  quarter  of  a  dram  of 
chlorate  of  potassa;  the  yellowish  mixture  smoulders 
to  a  red  powder,  which  must  be  well  washed  with 


LEAD. 


3C5 


water.  The  same  thing  happens  on  heating  the  li- 
tharge for  a  day,  but  not  to  the  melting  point,  and  at 
the  same  time  frequently  stirring  it.  In  both  cases  the 
litharge  receives  one  third  more  of  oxygen  ;  in  the  for 
mer  case  from  the  chloric  acid,  in  the  second  case  from 
the  air;  and  fe  thereby  converted  into  Pb^O^;  this 
compound  is  called  red  oxide  of  lead,  or  minium,  and  is 
much  used  as  a  scarlet  pigment. 

333.  Peroxide  of  Lead  (Pb  (X).  —  Experiment.  — 
If  you  heat  some  red  lefid  gently  'in  nitric  acid  for  a 
few  minutes,  it  is  resolved  into  an  oxide,  which  dis- 
solves, and  into  hi/peroxide  (Pb  CX),  which  remains  un- 
dissolved  as  a  dark-brown  powder.  Lead  is  one  of  the 
few  metals  which  combine  with  oxygen,  forming  hyper- 
oxides. 

•  Lead  and  Acids. 

334.  The  best  solvent  of  lead  is  nitric  acid.     Sul- 
phuric, phosphoric,  and  muriatic  acids  cannot  dissolve 
lead,  because  they  form  with  it  insoluble,  or  very  dilli 
cultly  soluble    salts.     As   protoxide    of   lead    is  easily 
made,  the  most  advantageous  method  of  preparing  the 
salts  of  lead  is  by  dissolving  the  protoxide  in  acids,  be- 
cause  that  portion  of  the  acid  is  thereby  saved  which 
would  otherwise  have  been  required  for  the  conversion 
of  the  lead  into  the  oxide  of  lead. 

Nitrate  of  Lead  ( Pb  O,  N  O5)  has  already  been  pre- 
pared in  two  ways  (§  160). 

335.  Sulphate  of  Lead  (Pb  O,  S  O0)  (§  173).— This  salt 
is  easily  formed  by  simple  or  double  elective  aiHnity, 
when  sulphuric  acid  or  sulphate  of  soda  is  added  to  a 
solution   of  lead.     Even    in    a  solution  of   lead   more 
than  a   thousand  times   diluted,  a  white  turbidness   is 
oroduced,  since  the  sulphate  of  lead  is  an  entirely  iu- 

31* 


366  HEAVY    METALS. 

soluble  salt ;  we  have,  accordingly,  in  sulphuric  acid,  a 
very  delicate  test  for  salts  of  lead.  This  salt  is  ob- 
tained in  great  quantities  in  print-svorks,  as  a  secon- 
dary product  in  the  preparation  of  the  acetate  of  alu- 
mina (alum  mordant)  from  sugar  of  lead  and  alum 
(§262). 

336.  Chloride  of  Lead  (Pb,  Cl).  —  Experiment.  — 
Heat  to  boiling  one  dram  of  litharge,  with  half  an 
ounce  of  muriatic  acid  and  half  an  ounce  of  water, 
and  decant  the  clear  liquid  *from  the  sediment  into 
a  glass  vessel ;  you  obtain,  on  cooling,  lustrous  white 
acicular  crystals  of  chloride  of  lead  (horn-lead).  This 
salt  is  but  very  sparingly  soluble  in  water. 

Experiment.  —  If  two  grains  of  litharge  and  fifteen 
grains  of  sal  ammoniac  are  fused  together  in  an  iron 
spoon,  there  is  obtained  a  combination  of  a  small 
quantity  of  chloride  of  lead,  with  a  large  proportion  of 
oxide  of  lead,  in  the  form  of  a  brilliant,  yellow,  lami- 
nated mass,  which  when  triturated  yields  a  handsome 
yellow  powder.  This  powder  is  used  by  painters  under 
the  name  of  Cassel  or  mineral  yellow. 

337.  Acetate  of  Oxide  of  Lead  (PbO,  A  +3  HO), 
combined  with  one  seventh  of  its  weight  of 
water  of  crystallization,  forms   the  most  im- 
portant  soluble   salt   of  lead,   sugar  of  lead 
(§  198),  which  commonly  crystallizes  in  four- 
sided  prisms.     On  exposure  to  the  air,  some 
of  its  acetic  acid  is  driven  off  by  the  carbonic 
acid  of  the  air,  and  the  salt  then  yields  with 
water  a  turbid  solution,  but   which  may  be  rendered 
transparent  by  adding  to  it  a  few  drops  of  acetic  acid. 

Basic  Acetate  of  Oxide  of  Lead  is  prepared  by 
digesting  a  solution  of  sugar  of  lead  with  oxide  of 
lead,  whereby  part  of  the  oxide  of  lead  is  dissolved 


LEAD.  367 

This  combination  is  kept  in  the  apothecaries'  shops  in 
a  liquid  form,  under  the  name  of  solution  of  subacetate 
of  lead,  or  GoularcFs  extract.  When  mixed  with  spring- 
water  it  forms  the  so-called  lead-water,  which  has  a 
milky  appearance,  because  some  carbonate  of  lead  is 
formed  and  separated  by  the  carbonic  acid  of  the 
water. 

338.  Tartrate  of  Oxide  of  Lead.  —  Experiment. — 
Mix  a  solution  of  two  grains  and  a  hatf  of  sugar  of 
lead  with  a  solution  of  one  grain  of  tartaric  acid ;  the 
white  precipitate  formed  is  collected  on  a  filter,  washed, 
and  dried ;  it  is  insoluble  tartrate  of  lead. 

Experiment.  —  Fill  a  small  phial  one  third  full  of  dry 
tartrate  of  lead,  and  heat  it  in  a 

Fig.  152.  ,  ,        ,  •     . 

sand-bath  over  a  spirit-lamp,  as 
long  as  fumes  continue  to  escape. 
These  have  an  empyreumatic 
odor,  and  burn  with  a  blue  flame, 
because  they  contain  much  car- 
bonic oxide  gas,  which  is  gener- 
ated by  the  carbonization  of  the 
tartaric  acid.  But  the  tartaric  acid 
contains  so  much  carbon,  that  a 
portion  of  it  remains  behind,  intimately  mixed  with 
the  metallic  lead.  The  black  substance  obtained  is  a 
pyrophoniS)  which  inflames  spontaneously  when  poured 
out  upon  a  stone,  because,  on  account  of  its  great  po- 
rosity, it  imbibes  oxygen  eagerly  from  the  air.  The  yel- 
low powder  produced  by  the  ignition  is  oxide  of  lead. 
If  the  phial  is  closed  while  it  is  yet  hot,  this  py 
rophorus  will  retain  its  inflammability  for  several  da  vs. 
Hydrate  of  Oxide  of  Lead.  —  Experiment.  —  By  add- 
ing ammonia  to  a  solution  of  sugar  of  lead  as  long  as 
a  precipitate  forms,  hydrate  of  oxide  of  lead  is  obtained 


368 


HEAVY     METALS. 


as  a  white  powder.     It   is  converted  by  heating  into 
yellow  anhydrous  oxide  of  lead. 

339.   Carbonate  of  the  Oxide  of  Lead  (Pb  O,  C  O.). 

Add  to  a  solution  of  sugar  of  lead  a  solution  of  car- 
bonate of  soda,  as  long  as  a  precipitate  is  formed  ;  the 
precipitate  is  carbonate  of  oxide  of  lead.  The  pigment 
known  under  the  name  of  ivhite  lead  is  likewise  car- 
bonate of  lead,  but  mixed  with  variable  quantities  of 
hydrated  oxide  of  lead  (basic  carbonate  of  lead).  This 
is  prepared  on  a  large  scale  in  different  ways. 

a.  According  to  the  English  method,  litharge  is  mixed 
with  vinegar  to  form  a  paste ;  this  is  then  spread  upon  a 
stone  slab,  and  exposed  to  the  fumes  of  burning  coke, 
the  carbonic  acid  of  which  combines  with  the  oxide- of 
lead.     The   acetic   acid   acts  in  this  case  the  part  of  a 
mediator.     Like   the  nitric   oxide  in  the  sulphuric-acid 
chambers,    it   dissolves    the    oxide    of    lead,    and    then 
tenders  it  to  the  carbonic  acid  ;  when  it  has  given  up 
the  first  portion,  it  dissolves  a  second,  &c.      It.  is  obvi- 
ous that  in  this  way  a  small  quantity  of  acetic  acid  (or 
else  of  sugar  of  lead)   is  sufficient  to  aid  in  converting 
gradually  a  large  quantity  of  litharge  into  white  lead. 

b.  By  the  oldest,  the   Dutch  method,  a  large  number 
of  jars,  in  which  some   vinegar   has   been   poured,  are 
arranged  in  a  building  upon  a  layer  of  stable-manure 
or  tan,  and  rolls   of  sheet-lead  are  then   suspended  in 
the  jars  above  the  vinegar,  and  the  whole  covered  with 
another  layer    of    stable-manure.     After   the   lapse    of 
several  months,  the  rolls  of  lead  are  found  to  be  mostly, 
if  not  entirely,  converted  into  white  lead.     The  manure 
is  decaying  straw,  the  spent  tan  is  decaying  wood;  de- 
cay is  a  slow  combustion,  or,  what  is  the  same  thing, 
a  slow  conversion  of  organic  substances  into  carbonic 


LEAD.  369 

acid  and  water.  In  every  combustion  or  decay,  heat  is 
liberated ;  this  in  the  present  case  is  sufficient  to  evapo- 
rate gradually  the  vinegar.  Accordingly,  oxygen,  aque- 
ous vapor,  fumes  of  vinegar,  and  carbonic  acid,  are 
present  in  the  air  of  the  white-lead  chambers.  If  you 
suppose  that  these  substances  combine  with  the  lead  in 
the  succession  just  mentioned,  the  following  order  of 
changes  will  take  place  :  —  1.  oxide  of  lead  ;  2.  hydrat- 
ed  oxide  of  lead;  3.  acetate  of  oxide  of  lead ;  4.  basic 
carbonate  of  oxide  of  lead.  Thus  there  is  formed  first 
oxide  of  lead,  which,  just  as  in  the  former  process,  is 
converted  into  carbonate  of  oxide  of  lead,  through  the 
mediation  of  acetic  acid.  The  finest  kind  of  white 
lead  is  that  of  Krems,  called  on  the  continent  of 
Europe  white  of  Kremnitz. 

c.  By  the  French  method,  the  white  lead  is  prepared 
in  the  moist  way  by  conducting  carbonic  acid  info  a 
solution  of  basic  acetate  of  lead  (Goulard's  extract). 
As  was  seen  above  (§  337),  a  solution  of  sugar  of  lead 
can  dissolve  still  another  atom  of  oxide  of  lead ;  this 
is  precipitated  by  the  carbonic  acid  as  white  lead, 
whereby  neutral  acetate  of  lead  is  once  more  formed 
in  the  liquid,  which  is  again' digested  with  litharge,  and 
afterwards  treated  with  carbonic  acid.  In  this  way  one 
pound  of  sugar  of  lead  may  be  made  gradually  to 
dissolve,  and  again  precipitate  as  white  lead  many 
pounds  of  litharge.  The  white  lead  obtained  by  this 
method  has  indeed  a  dazzling  white  color,  but  it  does 
not  possess  so  much  body  as  that  prepared  in  the 
English  or  Dutch  manner.  The  cheaper  sorts  are  ob- 
tained by  mixing  white  lead  with  powdered  sulphate  of 
baryta;  the  latter  remains  behind  when  white  lead  is 
dissolved  in  diluted  nitric  acid.  On  heating  white  lead, 
the  carbonic  acid  and  water  are  expelled,  and  the  yel- 
low residue  is  oxide  of  lead. 


370 


HEAVY     METALS. 


340.  Lead-Tree.  —  Experiment. —  Dissolve  half  an 
ounce  of  sugar  of  lead  in  six  ounces  of  water,  clarify 
the  liquid  by  adding  some  drops  of  acetic 
acid,  pour  it  into  a  phial,  and  then  sus- 
pend in  the  latter  a  zinc  rod,  by  attaching 
it  to  the  cork ;  the  zinc  is  soon  covered 
with  a  gray  coating,  from  which  brilliant 
metallic  spangles  will  gradually  shoot  forth, 
finally  filling  up  the  interior  of  the  phial. 
They  consist  of  pure  lead "  (the  lead-tree). 
After  twenty-four  hours,  no  trace  of;  lead  can  be  found 
in  the  solution  ;  it  has  been  replaced  by  the  acetate  of 
zinc;  the  stronger  zinc  has  abstracted  from  the  weaker 
lead  all  its  oxygen  and  acetic  acid.  By  this  experi- 
ment, not  only  the  difference  in  the  strength  of  affinity 
of  these  two  metals  is  clearly  shown,  but  it  beautifully 
illustrates  also  the  stochiometrical  law  of  chemical 
combination  and  decomposition  ;  for  it  is  only  neces- 
sary to  weigh  the  lead  formed,  and  the  piece  of  zinc 
before  and  after  the  experiment,  to  ascertain  that  the 
weight  of  the  precipitated  lead  is  to  the  loss  of  zinc  as 
1294  to  407.  An  atom  of  lead  has  thus  been  replaced 
by  an  atom  of  zinc. 

Lead  and  Sulphur. 

341.  Sulphuret  of  Lead  (Pb  S).  —  Experiment.  —  Add 
some  sulphuretted  hydrogen  to  a  solution  of  sugar  of 
.ead;  the  deep  black  precipitate  is  sulphuret  of  lead 
(§  133).  One  grain  of  sugar  of  lead  dissolved  in  two 
pounds  of  water  shows  itself  in  this  manner  by  a  brown 
colo*;  so  that  we  have  in  sulphuretted  hydrogen  an 
exceedingly  sensitive  test  for  salts  of  lead. 

In  this  combination,  namely,  as  sulphuret  of  lead,  we 
most  frequency  find  lead  in  nature,  and  from  it  alone 


LEAD.  371 

metallic  lead  is  obtained  on  a  large  scale.  This  ore  ia 
called  galena,  and  is  easily  recognized  by  its  grayish- 
black  color,  its  shining  metallic  lustre,  its  cubic  form, 
and  its  great  specific  gravity. 

342.  Preparation   of  Lead.  —  Sulphur   is   so   firmly 
combined  with  the  metals  in  the  sulphurets,  that  it  is 
impossible  to  expel  it  as  easily  as  oxygen,  for  instance, 
by  heating  it  with  coal.    Therefore  a  circuitous  method 
must  be  adopted ;  namely,  first  to  convert  the  metallic 
sulphuret  into  an   oxide  (roasting),  and  then  to  expel 
the  oxygen   (reduction).     To  effect  this,  the  galena  is 
heated  continuously  with  access  of  air,  whereby  both 
the  lead  and  the  sulphur  are  combined  with  oxygen. 
The  lead  is  converted  into  oxide  of  lead,  which  remains 
behind,  and  the  sulphur  into   sulphurous  acid,  which 
escapes ;  some   sulphate  of  lead  is  also  formed  at  the 
same   time.     The   roasted   galena   consists,   therefore, 
essentially  of  oxide  of  lead  (together  with  some  sul- 
phate of  lead) ;  this,  has  now  only  to  be  heated  with 
coal  in  a  flame  or  blast-furnace,  in  order  to  separate 
the  metallic  lead  (lead-works). 

A  second  mode  of  freeing  the  lead  from  sulphur 
consists  in  heating  the  galena  with  a  metal  which  has 
a  greater  affinity  for  sulphur,  and  replaces  the  lead. 
Such  a  metal  is  iron.  Iron  and  sulphuret  of  lead  are 
mutually  converted  into  lead  and  sulphuret  of  iron. 
The  iron  acts  here  just  in  the  same  way  that  the  zinc 
did  in  the  formation  of  the  lead-tree  ;  one  atom  of  iron 
replaces  one  atom  of  lead,  therefore  350  pounds  of  iron 
can  separate  or  throw  down  1294  pounds  of  metallic 
lead, 

343.  Lead  Shot.  —  Lead  may  be  granulated  by  pour- 
ing it  through  a  broom  into  water,  as  described  under 
zinc.     The  same  principle  is  applied  in  the  manufac- 


372  HEAVY    METALS. 

ture  of  shot)  only  that  an  iron  cullender  is  used  instead 
of  a  broom,  and  the  drops  of  lead  are  let  fall  from  such 
a  height,  that  they  solidify  before  reaching  the  water. 
For  making  the  largest-sized  shot,  a  tower  at  least  150 
feet  high  is  required.  A  small  quantity  of  arsenic  is 
usually  added  to  the  lead,  to  render  the  drops  perfectly 
globular.  As  lead  and  arsenic  are  both  inimical  to 
health,  shot  should  never  be  used  for  washing  out 
bottles. 

BISMUTH,  BISMUTHUM  (Bi). 
At.  Wt.  =  1330.—  Sp.  Gr.  =  9.8. 

344.  Bismuth  is  a  metal  chiefly  found  in   Saxony ; 
it  frequently  accompanies  the  cobalt  ores,  and,  as  al- 
ready mentioned,  in  the  smelting  of  this  ore  for  smalt, 
it  separates  as  cobalt-speiss,  nickel  also  being  generally 
present.     The  metal  is  procured  from  this,  and  also 
from  the  native  ore,  by  a  very  simple  process.     It  oc- 
curs both  in  the  ores  and  in  the  speiss  in  a  pure  state, 
when  it  melts  at  a  temperature  which  need  be  only  two 
and  a  half  times  higher  than  that  of  boiling  water ; 
consequently,  it  is  only  necessary  to  heat  the  ores  mod- 
erately upon  an  inclined  plate,  when  the  bismuth  melts 
and  flows  off  below,  while  the  other  metals  or  ores,  to- 
gether with  the  gangue,  remain  behind  unmelted.    This 
method  of  working  the  metal  is  called  eliquation.     Bis- 
muth is  brittle,  has  a  crystalline  laminated  texture,  and 
a  reddish-white  color. 

Experiments  with  Bismuth. 

345.  Experiment.  —  Heat  a  piece  of  bismuth  upon 
charcoal  before  the  blow-pipe;  it  melts  with  the  ejec- 
tion of  sparks,  and  volatilizes  at  a  higher  temperature 


BISMUTH.  373 

with  brisk  ebullition.  A  portion  of  the  fumes  condense 
on  the  charcoal,  coating  it  with  a  yellow  powder ;  this 
is  oxide  of  bismuth  (BI,  Oa).  If  you  throw  the  glowing 
metalli:  bead  into  a  small  paper  box,  it  divides  into 
small  globules,  which,  while  still  glowing,  will  skip 
about  for  some  moments.  An  odor  like  that  of  garlic, 
which  is  frequently  emitted  during  the  ignition,  proceeds 
from  arsenic,  small  quantities  of  which  occur  in  almost 
all  commercial  bismuth. 

346.  Experiment.  —  Melt  together  in  a  ladle  two  drams 
of  bismuth,  one  dram  of  lead,  and  one  drain  of  tin ;  the 
alloy  formed  has  the  very  remarkable   property  of  be- 
coming completely  liquid   when    thrown    into  boiling 
water.     Bismuth  melts  at  250°  C.,  lead  at  320°  C.,  tin 
at  230°  C.,  and  yet  the  mixture  of  these  three  metals 
melts  below  100°  C.      By  increasing  the  quantity  of 
lead,  alloys  may  be  prepared  which  readily  become  liquid 
^at  any  temperature  desired   above  100°  C.      They  are 

sometimes  employed  as  safety-plates  in  steam-boilers. 
The  heat  of  the  steam  increases  with  the  tension  of  the 
steam  in  the  boiler;  therefore  the  alloy,  to  be  used,  has 
only  to  be  so  selected  that,  in  case  of  a  too  great  in- 
crease of  steam,  the  plate  may  be  melted  by  the  heat 
of  the  steam  before  an  explosion  of  the  boiler  itself 
can  take  place.  As  these  alloys,  in  their  melted  state,  do 
not  burn  the  wood,  they  are  also  .very  well  adapted  for 
making  metallic  copies  of  engraved  wooden  moulds,  for 
calico-printing,  and  block-impressions.  This  alloy  is 
called  Rose's  metal,  after  the  inventor. 

347.  Experiment.  —  Bismuth  is  most  easily  dissolved 
by  nitric  acid.     Dissolve  some  bismuth  at  a  moderate 
heat  in  this  acid,  and  pour  the  solution  into  a  large  quan- 
tity of  water ;  it  becomes  very  turbid,  and  after  stand- 
ing; quietly,  a  white  precipitate  subsides,  which  contains 

32 


Bi2O3, 
Bi2  O3,       3 


3N06 


374  HEAVY    METALS. 

only  one  fourth  as  much  nitric  acid  as  the  sait  which 
crystallizes  out  from  the  bismuth  solution  when  you  let 
it  cool.     This  powder  is  subnitrate 
Acid  salt.    poiuWe.         of  oxide  of  bismuth,  and  is  used  as 
a   medicine.      A  small  proportion 
of  oxide  of  bismuth,  with  a  large 
proportion   of  nitric  acid,  remains 
Basic  salt,  insoluble.       dissolved  in  the  liquid.      The  an- 
nexed diagram  denotes  the  decom- 
position hereby  taking  place,  which  is  of  more  general 
interest,  as  showing  that  the  affinities  of  bodies  for  each 
other  may  be  changed  by  greater  or  less  dilution  with 
water. 

The  salts  of  bismuth  may  be  recognized  by  this  be- 
haviour with  water.  By  adding  sulphuretted  hydrogen 
to  the  solution  remaining  from  the  former  experiment, 
you  obtain  a  brownish-black  precipitate  of  sulphuret  of 
bismuth. 


COPPER,  CUPRUM  (Cu). 
At.  Wt.  =  396.  — Sp.  Gr.  =  8.8. 

348.  In  ancient  times  copper  was  chiefly  obtained 
from  the  island  of  Cyprus,  where  its  ores  were  found  in 
great  abundance  ;  this  explains  the  name,  cuprum.  It 
being  afterwards  deemed  expedient  to  give  mythologi- 
cal names  to  the  metals,  copper  received  the  name  of 
Venus,  the  protecting  goddess  of  Cyprus,  and  the  sign 
£.  Copper  possesses  several  excellent  properties, 
which  have  rendered  it  an  exceedingly  useful  metal. 

a.)  It  is  ductile  and  at  the  same  time  very  strong-  and 
tenacious,  so  that  it  may  be  hammered  out  into  plates, 
which,  even  when  very  thin,  still  hold  firmly  together. 

b.)   It  fuses  with  difficulty  (its  point  of  fusion  being 


COPPER.  375 

1200°  C.) ;  therefore  it  is  excellently  adapted  for  swcb 
articles  as  are  to  be  exposed  to  a  great  heat,  for  in 
stance,  kettles,  pans,  boilers,  moulds  for  casting,  &c. 

c.)  When  exposed  to  the  air,  it  suffers  from  rust  much 
less  ihan  iron ;  for  this  reason,  copper  utensils  are  much 
more  durably,  than  iron  ones.  Sheet-copper  is  em- 
ployed for  sheathing  ships,  and  for  roofing  towers  and 
other  buildings. 

d.)  It  is  quite  hard,  and  therefore  wears  out  but  slow- 
ly on  use,  as  in  copper  plates  for  engravings,  and  rollers 
of  print-works. 

e.)  With  zinc,  tin,  and  nickel,  it  forms  very  useful 
alloys,  such  as  brass,  tombee,  bronze,  bell-metal,  cannon- 
metal,  German  silver,  &c. 

/.)  It  is  precipitated  from  its  solutions  by  the  gal- 
vanic current  as  a  firm  coherent  mass ;  on  this  princi- 
ple, impressions  of  other  bodies  are  produced  by  the 
modern  process  of  electro-metallurgy. 

g.)  It  yields  with  oxygen  and  several  acids  insoluble 
combinations  of  a  beautiful  green  and  blue  color,  of  va- 
rious application  in  painting. 

Although  copper  possesses  no  smell,  yet  it  imparts  to 
moist  hands  and  to  the  water  which  has  long  been 
standing  in  vessels  made  of  it  (as  boilers  or  kettles),  a 
peculiarly  disagreeable  odor. 

Experiments  with  Copper. 

349.  In  the  moist  air,  copper  slowly  turns  gray  and 
afterwards  green  (native  mineral-green).  Copper,  like 
zinc,  attracts,  not  merely  oxygen  and  water,  but  also 
carbonic  acid  from  the  air;  the  green  coating  is  the 
liydrated  basic  carbonate  of  copper.  In  Siberia  this  com- 
bination occurs  in  large  beds  in  the  earth,  and  is  then 
called  malachite.  The  celebrated  Russian  copper  is  prin 


376  HEAVY     METALS. 

cipally  obtained  from  it ;  and  its  beautifully  mottled  va- 
rieties are,  like  marble,  formed  into  works  of  art,  and  are 
used  for  ornamenting  palaces,  &c.  This  green  body,  on 
receiving  yet  more  carbonic  acid,  acquires  a  beautiful 
blue  color,  and  is  converted  into  sesquibasic  carbonate  of 
copper,  which  likewise  occurs  native  as  a  copper  ore, 
under  the  name  of  blue  carbonate  of  copper.  The  arti- 
ficially prepared  is  called  mountain  blue,  and  is  em- 
ployed as  a  pigment,  particularly  for  painting  walls,  its 
color  not  being  changed,  like  Prussian  blue,  by  the  lime 
of  the  walls. 

350.  Experiment.  —  Hold  a  brightly  polished  copper 
coin  over  the  flame  of  a  spirit-lamp  ;  the  color  changes 
from  yellow  to  crimson,  violet,  and  blue,  and  finally 

passes  over  to  a  dark  gray. 
These  iridescent  hues  pre- 
sent a  particularly  beautiful 
appearance  by  holding  the 
coin  obliquely  in  the  mid- 
dle of  the  flame,  and  mov- 
ing it  to  and  fro;  in  the  cen- 
tre of  the  flame  the  coating 
vanishes,  but  it  instantane- 
ously reappears,  as  soon  as  the  coin  reaches  or  extends 
beyond  the  external  border  of  the  flame.  On  speed- 
ily quenching  the  coin  in  water,  it  becomes  brownish- 
red  ;  this  red  coating  is  suboxide  of  copper  (Cu2O). 
Such  a  coating  is  often  intentionally  produced  upon 
copper  medals,  as  it  is  less  liable  to  change  in  the  air 
than  the  brilliant  metallic  copper  (bronzing  of  copper, 
bronze  medals).  Suboxide  of  copper,  when  thrown 
into  melting  glass,  colors  it  blood-red  ;  in  this  manner  a 
beautiful  red  color  is  flashed  on  glass  in  the  glass  fac- 
tories. This  accounts,  also,  for  the  red  color  of  the  slag 


COPPER.  37? 

which  forms  during  the  calcination  and  fusion  of  cop- 
per. / 

351.  Protoxide   of  Copper  (CuO).  —  If   the   copper 
coin  is  left  for  some  time  in  the  point  of  the  flame,  it 
acquires    a    black    appearance;    protoxide  of  copper  is 
formed,  which  Jhas  a  black  color,  and  contains  as  much 
again    oxygen    as    the    red    suboxide.       If    suddenly 
quenched,  the  oxide   flies  off,  and  the  red  appearance 
of  the  coin    shows  that  the  suboxide  is   also  present 
beneath  the  film  of  the  protoxide.     By  long-continued 
ignition  the  whole  mass  of  the  coin  may  be  converted 
into  suboxide,  and  by  still  longer  heating,  completely, 
at  last,  into  protoxide.     The  glowing  cinders,  which  fall 
off  in  the  workshops  of  the  coppersmith  (copper  scales), 
consist   of  a    mixture    of  the    suboxide  with   the  pro- 
toxide. 

Experiment.  —  Triturate  a  small  quantity  of  borax 
with  a  scale  of  the  black  oxide  of  copper,  and  melt  it 
into  a  bead  on  a  platinum  wire  before  the  blow-pipe ; 
the  oxide  of  copper  will  dissolve  in  the  borax,  and  form 
a  green  glass.  Oxide_.of  copper  is  made  use  of  in  glass 
and  porcelain  painting.  If  introduced  into  the  interior 
flame,  the  green  color  passes  over  to  red,  because  the 
oxide  is  there  reduced  to  suboxide  of  copper. 

Oxides  of  copper  may  also  easily  be  prepared  in  the 
humid  way,  but  they  have  then  a  very  different  color. 

352.  Hydrated  Oxide  of  Copper  (Cu  O,  H  O).  —  Ex- 
periment. —  Add  to  a  solution  of  the  previously  men- 
tioned blue  vitriol,   or   sulphate    of  copper,  a    solution 
of  caustic  potassa;  a   greenish-blue  powder  is   precipi- 
tated ;  it  is  hydrated  oxide  of  copper.     The  black  oxide 
yields,   also,  chemically  combined  with  water,  a   blue 
body.     Mixed  with   gypsum  this  forms  a  light  powder, 
the  well-known   Bremen  blue.      Boil   a  portion  of  '.he 

32* 


378  HEAVY     METALS. 

liquid;  the  precipitate  will  become  black,  because  at 
the  boiling  point  the  combination  between  the  oxide 
of  copper  and  the  water  is  destroyed ;  —  another  exam- 
ple of  chemical  decomposition  occasioned  by  mere  ele- 
vation of  temperature. 

353.  Ammoniated  Oxide  of  Copper.  —  Experiment.  — 
Repeat  the  former  experiment,  but  instead  of  potassa 
take  ammonia;  here  also  the  hydrated  oxide  of  cop- 
per   is   first   precipitated,   but   this   is   redissolved   by 
adding  more   ammonia,  forming  a  superb  blue  liquid. 
Ammonia    is    therefore    a   test    for    salts   of   copper. 
Pour  upon  the  blue  liquid  an  equal  quantity  of  strong 
alcohol,  and  direct  the  stream  against  the  side  of  the 
glass,   so  that  the   alcohol  may  float  on  the  surface; 
after  the  lapse  of  twenty-four  hours,  a  mass  of  dark- 
blue  acicular  crystals  is  perceptible,  which  consist  of 
a  combination  of  sulphate  of  copper  with  ammonia, 
and  are  called  ammonio- sulphate  of  copper.     By  dissolv- 
ing them  in  water,  the  blue  liquid  of  the  apothecaries' 
show-bottles  is   prepared.       The   alcohol   effects   that 
which  is  otherwise  attained  by  boiling,  namely,  a  re- 
moval of  the  water ;  it  withdraws  from  the  blue  liquid 
a  portion  of  its  water,  and  the  double  salt,  which  is  in- 
soluble in  alcohol,  is   separated.     The  water  may  be 
abstracted,  also,  in  this  way  from  other  solutions  of 
salts,  which  would  undergo  a  decomposition  on  the 
evaporation  of  the  water  by  heat. 

354.  Experiment.  —  Add  to  a  diluted  solution  of  blue 
vitriol  a  small  quantity  of  pulverized  sugar  of  milk,  and 
then  rather  more  liquid  potassa  than  is  necessary  to 
precipitate  the  hydrated  oxide  of  copper,  and   heat  the 
mixture  ;  the  blue  color  will  soon  pass  into  a  yellow 
ish-red.       The  yellowish-red  precipitate  is  suboxide  oj 
copper,  which  is  formed  from  the  protoxide  of  copper, 


COPPER.  379 

because  the  sugar  is  able  to  abstract  from  the  latter 
half  its  oxygen.  The  same  compound,  but  of  a  more 
beautiful  red  color,  is  obtained  by  boiling  verdigris  with 
vinegar,  and  then  adding  some  honey  to  the  solution 
obtained,  and  again  boiling.  Thus  is  easily  explained 
why  a  red  deposit  always  subsides  from  the  oxymel  of 
subacetate  of  copper  in  the  apothecaries'  shops  ;  in  the 
slow  separation  which  occurs  in  the  latter  case,  small 
distinct  crystals  are  frequently  formed. 

Reduction  of  the  Copper  Compounds  to  Metals. 

355.  Experiment.  —  Rub  together  some  grains  of  blue 
vitriol,    carbonate   of  soda,    and   charcoal;   ignite  the 
mixture  strongly  for  some  minutes  before   the  blow- 
pipe, and  then  elutriate  the  black  mass  with  water; 
numberless  small  spangles  of  metallic  copper  will  re- 
main behind  on  the  bottom  of  the  vessel.      The  car- 
bonate of  soda  takes  the   sulphuric  acid  from  the  blue 
vitriol,  and  the  charcoal  the  oxygen  from  the  oxide  of 
copper. 

356.  Experiment.  —  If  half  an  ounce  of  blue  vitriol  is 
heated  to  boiling  with  an  ounce  and  a  half  of  water  in 
a  porcelain  bowl,  and  then  boiled  a  few  minutes  with 
some  granulated  zinc,  the  metallic  copper  separates  as 
a  powder,  since   the   zinc  has  a  greater   affinity  than 
copper  for  oxygen  and  for  sulphuric  acid.     The  pow- 
der  obtained   is  washed,  and  then  boiled  with  water 
and  a  few  drops  of  sulphuric  acid,  in  order  to  remove 
all  the  zinc.     It  must  be  dried  quickly,  but  not  at  a 
high  heat,  for  copper   in  this    state   of  minute   subdi- 
vision attracts  oxygen  ^yith  more    avidity  than  when 
it  is  in  a  compact  mass. 

357.  Experiment.  —  Introduce  some  hydrated  oxide 
of  copper   into   a   test-tube,  the  bottom  of  which    if 


380 


HEAVY     METALS. 


Fig.  156. 


broken  out,  heat  it,  and  then  pass  over   it   a  stream 
Fig  155  of    hydrogen,    which     is 

evolved  by  zinc  and  di- 
luted sulphuric  acid;  in 
the  heat,  the  hydrogen 
abstracts  from  the  oxide 
of  copper  its  oxygen,  and 
forms  with  it  water,  which 
escapes  in  company  with 
the  hydrated  water.  This 
method  is  frequently  employed  for  the  reduction  of 
ores  on  a  small  scale. 

358.  Experiment.  —  Push  an  iron  rod  into  a  good- 
sized,  large-mouthed  phial,  forcibly  enough 
to  break  out  the  bottom,  file  off  the  sharp 
edges  of  the  fractured  part,  and  bind  a 
moistened  bladder  over  the  mouth  of  the 
phial.  Then  twist  a  wire  firmly  round 
the  phial,  in  such  a  manner  as  to  form  two 
or  three  supports,  by  means  of  which  it 
may  be  suspended  in  a  tumbler. 

Let  a  strip  of  strong  sheet-zinc,  of  the 
width  of  the  finger,  and  five  inches  long, 
be  soldered  to  a  strip  of  thin  copper  plate, 
ten  inches  long,  and  bend  the  strip  of  cop- 
per as  represented  in  the  annexed  figure. 
Put  a  coin  upon  the  lower  horizontal  part 
of  the  copper  strip,  —  for  instance,  a  bright  dollar,  —  or 
some  other  metallic  object,  the  impression  of  which  you 
wish  to  have.  Now  fill  the  phial  three  quarters  full  with 
very  diluted  sulphuric  acid  (onqgitlram  of  sulphuric  acid 
to  two  ounces  of  water),  introduce  the  zinc,  and  sus- 
pend the  apparatus  in  a  tumbler,  in  which  a  saturated 
solution  of  blue  vitriol,  and  also  a  few  whole  crystals 


Fig.  157. 


COPPER.  381 

Fig.  158.  of  blue  vitriol,  have  been  put.     In  the 

course  of  a  few  minutes  the  coin  will 
be  covered  with  a  thin  film  of  metallic 
copper,  and  after  several  days  with  a 
layer  several  lines  in  thickness,  which 
may  be  removed  as  a  coherent  mass. 
Tallow  and  wax  must  be  smeared 
over  those  parts  of  the  coin  and  plate 
on  which  the  copper  is  not  to  be  deposited.  The  sunk 
impression  thus  obtained  may  be  used  in  the  same 
way  again,  instead  of  the  coin,  as  a  mould  for  obtain- 
ing a  raised  impression.  When  the  evolution  of  the 
gas  in  the  phial  has  ceased,  a  few  drops  of  strong  sul- 
phuric acid  may  be  stirred  in,  or  the  liquid,  which  con- 
tains sulphate  of  zinc  in  solution,  may  be  replaced  by 
a  fresh  supply  of  diluted  sulphuric  acid.  Salt  water 
may  also  be  used  instead  of  sulphuric  acid,  but  then 
the  separation  of  the  copper  takes  place  more  slowly. 

The  decomposition  of  the  blue  vitriol  has,  in  this 
case,  been  effected  by  the  galvanic  current,  which  is 
always  generated  when  different  kinds  of  metals  come 
in  contact,  or  are  introduced  into  different  liquids.  The 
bladder  is  a  porous  substance,  through  which  the  gal- 
vanic current  may  pass.  Galvanism  here  takes  the 
place  of  the  plastic  artist,  and  hence  the  term  galvano- 
plastic,  applied  in  Germany  to  electro-metallurgy.  A 
solution  of  gold  or  silver  may  be  decomposed  in  the 
same  manner  (galvanic  gilding  and  silvering). 

Copper  and  Acids. 

359.  Cliloride  of  Copper  (Cu  Cl).  —  Experiment.  —  If 
muriatic  acid  is  added  to  oxide  of  copper,  a  green  so- 
lution is  obtained,  and  from  it,  by  evaporation,  a  green 
salt,  chloride  of  copper,  or  muriate  of  oxide  of  copper 


382 


HEAVY    METALS. 


Introduce  some  of  it  into  the  wick  of  a  spirit-lamp ;  it 
dissolves  in  the  alcohol,  and  colors  the  flame  green. 
Write  on  paper  with  a  very  diluted  solution  of  it ;  the 
color  of  the  writing  changes  on  heating,  and  again  on 
cooling,  as  in  the  case  of  chloride  of  cobalt  (§  308). 
Metallic  copper  is  dissolved,  but  very  slowly,  and  with 
access  of  oxygen. 

For  Sulphate  of  Oxide  of  Copper,  or  Blue  Vitriol,  see 
§175. 

360.  Nitrate  of  Oxide  of  Copper  (Cu  O,  N  O5  +  5  HO) 
Copper  dissolves  very  readily  in  nitric  acid,  forming 
a  blue  liquid  (§  162) ;  if  the  solution  is  set  aside  in  a 
warm  place,  blue  crystals  of  nitrate  of  copper  are  depos- 
ited, which  deliquesce  in  the  air.  The  accompanying 

diagram  serves  to 
Volatile,  illustrate  the  pro- 
cess attending  the 
solution  of  copper, 
as  well  as  of  most 
vSatV  other  metals,  in  ni- 
tric acid.  It  is  al- 
ready known  that  the  nitric  oxide  gas  which  escapes 
becomes  nitrous  acid  on  coming  into  contact  with  the 
air. 

Experiment.  —  Envelop  quickly  in  tinfoil  some  crys- 
tals of  nitrate  of  copper,  moistened  with  a  drop  of  wa- 
ter, and  press  the  parcel  compactly  together,  and  put  it 
upon  a  stone ;  flames  and  smoke  will  soon  break  forth 
from  the  bubbling  mass,  because  the  tin  overpowers 
the  nitric  acid,  and  by  means  of  its  oxygen  becomes 
oxidized  into  oxide  of  tin. 

Oxide  of  copper  forms,  with  phosphoric,  arsenic,  ox- 
alic, and  silicic  acids,  insoluble  blue  or  green  com- 
pounds, in  the  same  way  as  with  carbonic  acid. 


COPPER.  383 

361.  Verdigris.  —  Experiment.  —  By  sprinkling  a 
Copper  coin  from  time  to  time  with  vinegar,  it  becomes 
gradually  covered  with  a  green  coating.  When  copper 
is  rusted  merely  by  exposure  to  the  moisture  of  the  at- 
mosphere, or  of  the  earth,  basic  carbonate  of  copper  is 
formed;  but  \^hen  the  rusting  is  effected  by  vinegar, 
basic  acetate  oj  copper  is  formed.  The  latter  is  the  ver- 
digris of  commerce.  It  is  prepared  on  a  large  scale, 
either  directly  from  copper  and  vinegar  (green  or  Ger- 
man verdigris),  or  indirectly  by  packing  sheets  of  cop- 
per with  the  refuse  of  pressed  grapes,  since  the  juice  yet 
adhering  to  the  mash  gradually  passes  over  into  vin- 
egar (blue  or  French  verdigris).  Verdigris  boiled  with 
vinegar  gives  a  blue  solution,  from  which,  on  cooling, 
dark  green  crystals  of  neutral  acetate  of  oxide  of  copper 
(Cu  O  A  -f-  HO)  are  deposited  (crystallized  or  distilled 
verdigris). 

Verdigris,  like  all  the  salts  of  copper,  is  very  poison- 
ous;  the  white  of  eggs  and  milk  are  efficacious  anti- 
dotes. Polished  iron,  ammonia,  sulphuretted  hydrogen, 
and  especially  ferrocyanide  of  potassium  (§  292),  serve 
for  the  detection  of  salts  of  copper. 

Copper  and  Sulphur. 

362.  Experiment.  —  If  some  sulphuretted  hydrogen 
water  is  added  to  a  solution  of  any  of  the  copper  salts, 
a  black  precipitate  of  sulphur et  of  copper  is  produced 
(§  131).  Heat  this,  after  it  has  settled  and  the  liquid 
has  been  decanted,  with  some  drops  of  nitric  or  muriatic 
acid  ;  the  sulphuret  of  copper  is  decomposed  and  dis- 
solved, while  nitrate  or  muriate  of  copper  is  formed. 
This  mode  is  universally  employed  on  a  small  scale, 
especially  in  analysis,  in  order  to  convert  metallic  sul- 
phurets  into  soluble  salts. 


384  /'HEAVY    METALS. 

363.  Preparation  of.  Copper.  —  The  sulphuret  of  cop- 
per is  the  most  common  ore  from  which  copper  is  ex- 
tracted. It  is  seldom  found  pure,  but  mostly  combined 
with  sulphuret  of  iron,  as  in  copper  pyrites.  The  pro- 
cess of  the  reduction  and  smelting  of  copper  is,  accord- 
ingly, very  tedious,  as  not  only  the  sulphur,  but  also  the 
iron,  must  be  got  rid  of.  This  is  effected,  —  1st,  by 
roasting  in  the  air,  whereby  the  copper  is  converted 
into  oxide  of  copper,  the  iron  into  black  oxide  of  iron, 
and  the  sulphur  into  sulphurous  acid ;  2d,  by  melting 
the  roasted  ore  with  charcoal  and  some  silicious  sub- 
stance, by  which  means  metallic  copper  and  carbonic 
oxide  are  formed  from  the  oxide  of  copper  and  the  char- 
coal, and  silicate  of  protoxide  of  iron  (iron  slag)  from 
the  protoxide  of  iron  and  quartz.  What  appears  thus 
simple  is,  in  reality,  so  difficult  an  operation,  that  the 
roasting  and  melting  must  often  be  alternately  repeated 
ten  or  twenty  times  in  order  to  remove  all  the  iron  and 
sulphur.  The  melted  mass,  which  is  obtained  when 
about  half  the  iron  and  sulphur  is  abstracted,  is  called 
matte  (crude  copper)  ;  and  black  copper,  when  it  contains 
only  about  five  per  cent,  of  these  two  substances.  The 
complete  refining  of  black  copper  is  effected  by  melting 
the  metal  again,  exposing  it  at  the  same  time  to.  the 
action  of  the  air,  whereby  the  iron,  sulphur,  and  other 
foreign  metals  which  may  be  present,  as  lead  and  anti- 
mony, are  oxidized  before  the  copper.  When  the  black 
copper  contains  silver,  it  is  subjected  to  the  process  of 
liquation. 

The  operation  of  working  the  copper  is  much  easier 
when  the  ores  are  combined  with  oxygen  instead  of 
sulphur,  as  they  yield  the  metallic  copper  by  merely 
heating  with  coal ;  but  such  ores  are  of  too  rare  occur- 
rence in  nature  to  yield  sufficient  copper  to  meet  the 
demand. 


MERCURY.       *  385 

364.  Alloys  of  Copper.  —  Copper  forms  very  impor- 
cant  alloys  with  several  other  metals. 

Gold  and  copper  form  the  common  gold,  silver  and 
copper  the  common  silver,  from  which  gold  and  silver 
articles  and  coins  are  made. 

The  well-known  brass,  and  other  metallic  compounds 
having  the  appearance  of  gold,  such  as  tombac,  sim- 
ilor,  prince's  metal,  red  brass,  &c.,  are  composed  of 
zinc  and  copper.  Spurious  gold-leaf  is  made  by  ham- 
mering out  tombac  into  exceedingly  thin  leaves,  which, 
when  finely  pulverized,  constitutes  the  so-called  gold 
bronze.  Purple  or  copper  bronze  is  prepared  by  gently 
heating  the  gold-colored  bronze  till  it  turns  to  a  purple- 
red  color. 

Zinc,  nickel,  and  copper  constitute  the  ingredients  of 
German  silver  (packfong,  white  copper). 

Tin  and  copper  form  a  very  hard  gray  alloy,  from 
which  statues,  cannons,  bells,  mirrors,  &c.,  are  cast 
(bronze,  gun-metal,  bell-metal,  speculum  metal). 

MERCURY,  HYDRARGYRUM   (Hg). 
At.  Wt.  =  1250.  —  Sp.  Gr.  =  13.5. 

365.  We  have  in  mercury  the  only  metal  which  is 
fluid  at   ordinary  temperatures;   for  this  reason,   and 
also  on  account  of  its  silver-white  brilliancy,  it  has  been 
called  hydrargyrum  (water-silver  or  liquid  silver).     But 
subsequently,   from  its  mobility,  it  was  dedicated  to 
Mercury,  the  most  active  of  the  ancient  gods,  and  re- 
ceived his  name,  the  symbol  $  being  at  the  same  time 
assigned  to  it.     Even  now,  quicksilver  and  its  various 
medicinal  preparations,  such  as  calomel  and  corrosive 
sublimate,  are  called  mercurial  remedies.     In  the  north- 
ern parts  of  Siberia  mercury  becomes  solid  every  winter, 

33 


386 


HEAVY    METALS. 


whenever  the  cold  reaches  — 40°  C.,  or  — 32°  R,.,  but  in 
our  climate  it  can  only  be  solidified  by  artificial  frigo- 
rific  mixtures.  Its  action  in  the  heat  also  corresponds 
with  this ;  namely,  it  boils  at  360°  C.  (consequently 
with  only  three  and  a  half  times  greater  difficulty  than 
water),  and  it  is  therefore  easily  volatilized  and  dis- 
tilled. 

Experiment.  —  Fasten  to  the  cork  of  a  phial  contain- 
ing mercury  a  piece  of  wood,  affixing  to  the  bottom  of 
the  latter  some  genuine  gold-leaf ;  the  gold,  after  some 
days,  will  have  assumed  a  white  color,  and  be  converted 
into  an  alloy  of  gold  and  mercury.  It  is  obvious  from 
this,  that  fumes  of  mercury  must  be  contained  in  the 
air  of  the  phial,  and  that  mercury,  like  water,  evaporates 
slowly  even  at  ordinary  temperatures.  The  vapor  of 
mercury,  and  the  preparations  of  mercury,  are  very  in- 
jurious ;  they  first  produce  involuntary  salivation,  and 
afterwards  lingering,  dangerous  maladies  ;  therefore, 
in  experimenting  with  mercury,  not  only  the  inhalation 
of  the  fumes  should  be  avoided,  but  it  must  be  weighed 
and  decanted  over  a  bowl,  so  that,  if  any  portion  of  it 
should  happen  to  be  spilt,  it  may  not  fall  upon  the  floor. 
Spirit-thermometers  only  should  be  suspended  in  sleep- 
ing-apartments and  sitting-rooms,  since,  from  the  acci- 
dental breaking  of  the  mercurial  thermometer,  the  at- 
mosphere would  be  vitiated  by  the  mercury  running 
into  the  chinks  of  the  boards,  from  which  it  could 
be  removed  only  with  great  difficulty.  The  same  rule 
applies,  too,  to  green-houses,  as  the  fumes  of  mercury 
are  also  poisonous  to  plants.  As,  in  comparison  with 
water,  mercury  boils  at  a  very  high,  and  freezes  at  a 
very  low  temperature,  and  as  it  has  a  great  specific 
weight,  it  is  for  these  reasons  excellently  adapted  to  the 
construction  of  thermometers,  barometers,  areometers, 


MERCURY. 


&c.  (§§  16,  24,  93).  Its  chief  use  in  areometers  is  tc 
lower  the  centre  of  gravity,  thereby  forcing  the  instru- 
ment to  float  in  an  upright  position.  In  the  less  ac- 
curate areometers,  lead  shot  are  frequently  substituted 
for  mercury 

Mercury  and  Acids. 

366.  Mercury,  if  quite  -pure,  retains  its  metallic  lustre 
in  the  air  and  water,  and  it  is  therefore  ranked  among 
the  noble  metals  ;  but  if  it  is  mixed  or  adulterated  with 
other  metals,  as  lead,  tin,  or  bismuth,  a  gray  film  will 
gradually  form  upon  its  surface.     On  account  of  the 
slight  affinity  of  the  noble  metals  for  oxygen,  their  ox 
ides  cannot  be  prepared  directly  by  exposing  them  ti 
the  air,  or  by  heating  them  to  redness,  but  only  indi 
rectly,  the  best  way  being  to  treat  the  metals  with 
acids.     The  most  powerful  solvent  for  mercury  is  nitric 
acid  ;  the  cheapest  is  sulphuric  acid. 

367.  Nitrate  of  Suboxide  of  Mercury  (Hg>  O,  N  O5). 
—  Experiment.  —  Pour  into,  a  porcelain  dish  one  ounce 
of  mercury,  one  dram  of  water,  and  half  an  ounce  of 
nitric  acid  ;  cover  the  vessel  and  place  it  aside  for  sev- 
eral days  ;  you  will  then  find  the  mercury  covered  with 
white  crystals  ;  they  are  the  nitrate  of  the  suboxide  of 
mercury.     In  the  cold,  two  atoms  of  mercury  take  up 
only  one  atom  of  oxygen  ffom  the  nitric  acid.     Pat  a 
part  of  the  crystals  into  a  phial,  and  pour  over  them 
some  water  ;  a  milky  turbidness  is  produced,  as  in  the 
solution  of  bismuth  (§  347),  but  it  disappears  again  on 
the  addition  of  a  few  drops  of  nitric  acid. 

This  solution  of  suboxide  of  mercury  serves  for  the 
following  experiments  :  — 

368.  Suboxide  of  Mercury  (Hg2  O).  —  Experiment.  — 
To  a  part  of  the  solution  of  suboxide  of  mercury  is 


388  HEAVY     METALS. 

added  a  solution  of  potassa  ;  a  black  precipitate  of  sub* 
oxide  of  mercury  is  formed.  This  preparation  must  be 
kept  in  an  opaque  phial,  because  it  is  resolved  by  the 
light  into  oxide  of  mercury  and  metallic  mercury.  If 
ammonia  is  used  instead  of  the  potassa,  a  triple  com- 
bination is  obtained  of  suboxide  of  mercury,  ammonia, 
arid  nitric  acid,  —  black  or  Hahnemann's  suboxide  of 
mercury,  used  in  Germany  as  a  medicine. 

369.  Experiment.  —  If  a  drop  of  the  solution  of  mer- 
cury is  rubbed  upon  a  copper  coin,  the  mercury  separates 
as  a  metal,  and  effects  a  false  silvering-  of  the  copper. 

Experiment.  —  Make  a  stroke  across  a  brass  plate 
with  a  wooden  stick  that  has  been  dipped  in  the  solu- 
tion of  mercury ;  if  the  plate  is  afterwards  bent  at  this 
place  it  will  break,  as  though  it  had  been  cut ;  because 
the  reduced  mercury  penetrates  the  brass  with  great 
quickness,  and  renders  it  brittle.  Thus  the  brazier  can 
make  use  of  this  solution  instead  of  shears. 

370.  Subchloride  of  Mercury  (Hga  Cl).  — Experiment. 
—  Add  some  muriatic  acid,  or  a  solution  of  common 
salt,  to  a  part  of  the  diluted  solution  of  the  suboxide  of 
mercury;  a  heavy  white  precipitate  of  muriate  of  sub' 
oxide  of  mercury,  or  subchloride  of  mercury r,  is  produced, 
which  is  insoluble  in  water.     When  finely  washed  and 
dried,  this  salt  of  mercury  forms  the  highly  important 
medicine  known  as  calomel  (precipitated).     If  some  of 
it  is  moistened  with  potassa  or  lime  water,  it  becomes 
black,  owing  to  the  suboxide  of  mercury  being  set  free; 
thus  is  explained  the  Greek  name  calomel  («aXos,  beau- 
tiful, /Lie'Aas,  black).     This  combination  is   also  slowly 
decomposed  by  light.     Formerly,   subchloride   of  mer- 
cury was  universally  prepared  from  chloride  of  mercury 
and  metallic  mercury,  which  were  rubbed  together  and 
sublimed  (sublimed  calomel).     By  this  process   Hg  C* 


MERCURY, 


and  Hg  are  converted  into  Hg.  Cl,  a  heavy,  crystalline; 
white  mass,  whhh  is  pulverized  and  washed  out  many 
times  with  boL.ng  water.  The  powder  thus  obtained 
has  a  slight  yellowish  tinge. 

371.  Nitrate   of  the    Peroxide    of  Mercury    (Hg  O, 
N  OJ.  —  Experiment.  —  Dissolve  in  a  flask,  at  a  moder- 
ate heat,  some  mercury  in  nitric  acid,  and  when  com- 
pletely dissolved,  boil  the  liquid  briskly  for  some  min- 
utes.    While   boiling,  the   mercury  combines  with  as 
much  again  oxygen  as  in  the  cold,  and  accordingly  ni- 
trate of  peroxide  of  mercury  is  produced,  which  crystal- 
lizes from  the  liquid  on  cooling.     A  solution  of  this  salt 
gives,  with  potassa  or  lime-water,  a  yellowish-red  pre- 
cipitate of  peroxide  of  mercury,  but  it  is  not  rendered 
turbid  by  muriatic  acid  or  common  salt. 

372.  Peroxide  of  Mercury  (HgO).  —  Experiment. — 
Pleat  gradually  in  a  test-tube  some  of  the  crystals  of 
the  nitrate  of  peroxide  of  mercury,  till   they  cease  to 
give  off  fumes ;  the  nitric  acid  escapes,  partly  decom- 
posed into  nitrous  acid,  the  oxide  of  mercury  remains 
behind.     Its  red  color,  however,  appears  first  on  cool- 
ing; as  long  as  it  is  hot,  it  looks  black.     It  is  resolved 
by  too  strong  a  heat  into  oxygen  and  metallic  mercury 
(§56). 

373.  Perchloride  of  Mercury  (Hg  Cl).— Experiment,— 
Heat  some  peroxide  of  mercury  with  muriatic  acid,  and 
continue  adding  the  latter  till  a  complete   solution   is 
obtained;  the  white  prismatic  crystals  which  separate, 
on  cooling  are  muriate  of  peroxide  of  mercury,  or  per" 
chloride  of  mercury,  —  one  of  the  most  violent  poisons. 
The  same  compound  is  obtained   on   a  large  scale,  in 
white,  transparent,  heavy  masses,  by  the  sublimation  of 
the  sulphate  of  oxide  of  mercury  with   common  salt; 
hence  its  common  name    corrosive  sublimate  (mercurius 

33* 


390  HEAVY    METALS. 

sublimatus  corrosivus).  Potassa  turns  calomel  black, 
but  corrosive  sublimate  yellowish-red.  Poisonous  sub- 
stances commonly  have  the  property  of  protecting  veg- 
etable and  animal  substances  from  decay,  and  perchlo- 
ride  of  mercury  possesses  this  power  in  a  high  degree. 
For  this  reason,  wood  for  ship-building,  and  sleepers  for 
railroads,  are  saturated  with  a  solution  of  it  in  water 
(Ky anizing')  ;  the  plants  of  herbariums  are  passed 
through  a  solution  of  it  in  alcohol,  &c.  It  must  not  be 
forgotten,  that  these  things  themselves  are  thereby  ren 
dered  poisonous.  In  cases  of  poisoning,  large  quan- 
tities of  whites  of  eggs  must  immediately  be  adminis- 
tered, as  the  albumen  forms  with  the  chloride  of  quick- 
silver an  insoluble  compound. 

374.  If  ammonia  is  added  to  a  solution  of  perchloride 
of  mercury,  then  red  oxide  is  not  precipitated,  but  a 
white  body,  which  is  likewise  (as  in  §  368)  a  triple 
compound,  consisting  of  mercury,  chlorine,   and  am- 
monia.    It  is  kept  in  the  apothecaries'  shops  as  an  ex- 
ternal remedial  application,  under  the  name  of  white 
precipitate. 

375.  Experiment.  —  Add  some  salt  of  tin  (protochlo- 
ride  of  tin)  to  another  portion  of  the  solution,  and  heat 
the  liquid  ;  a  gray  powder  will  separate ;  this  is  mercury 
in  a  state  of  extreme  comminution.     If  you  boil  it  with 
muriatic    acid,    after  having   decanted  the    liquid,  the 
powder  finally  forms  into  globules.     The  protochloride 
of  tin  has  so  strong  a  tendency  to  pass  over  into  per- 
chloride, that  it  abstracts  the  chlorine  from  the  chloride 
c  f  mercury.     This  action  is  made  available  in  analysis 
for  detecting  the  salts  of  mercury. 

Mercury  may  be  minutely  divided  also  by  long  tritu- 
ratio'n  with  viscous  substances,  as  fat,  tallow,  wax,  &c.t 
so  that  no  particles  of  it  can  be  discerned  by  the  naked 


MERCURY.  391 

eye.     In  this  manner,  mercurial  ointment  and  mercuria! 
pla  ters  are  prepared  by  the  apothecaries. 

Mercury  and  Sulphur. 

376.  Sulphur et  of  Mercury  (Hg  S). —  Experiment. — 
If  a  solution  of  chloride  of  mercury  is  agitated  with  a 
little  sulphuretted  hydrogen  water,  or  sulphuret  of  am- 
monium, a  white  precipitate  is  formed,  which,  on  add- 
ing more  of  the  precipitating  body,  becomes  yellow, 
brown,  and  finally  black ;  the  black  substance  is  sul- 
phuret of  mercury.  This  compound  is  also  obtained  by 
mixing  mercury  with  melted  sulphur,  or  indeed  by  rub- 
bing it  for  a  day  with  flowers  of  sulphur  (Ethiops  min- 
eral). If  this  black  sulphuret  of  mercury  is  sublimed 
in  a  glass  tube,  then  a  blackish-red  crystalline  mass  is 
obtained,  the  color  of  which,  by  friction,  passes  over 
into  the  most  magnificent  scarlet-red.  The  sulphuret 
of  quicksilver  in  this  state  is  called  vermilion,  or  cinna- 
bar. The  red  and  the  black  sulphuret  of  mercury  have 
precisely  one  and  the  same  composition,  and  yet  a  very 
great  difference  in  appearance ;  they  afford  one  of  the 
finest  examples  of  isomeric  combinations.  In  both  the 
red  and  black  sulphuret  of  mercury,  one  atom  of  sul- 
phur is  always  combined  with  one  atom  of  mercury,  or 
one  ounce  of  sulphur  with  6^  ounces  of  mercury.  Ver- 
milion is  also  frequently  prepared  in  factories  in  the 
moist  way,  by  triturating  together  for  a  day  mercury, 
sulphur,  and  a  solution  of  potassa.  When  vermilion  is 
pure,  it  volatilizes  completely  on  a  glowing  coal,  emit- 
ting, at  the  same  time,  a  blue  sulphurous  flame ;  but  if 
adulterated  with  minium,  beads  of  metallic  lead  remain 
behind.  On  account  of  its  insolubility,  it  is  far  less 
prejudicial  to  health  than  the  other  compounds  of 
mercury. 


392  HEAVY    METALS. 

Cinnabar  also  occurs  in  nature,  arid  we  have  in  ft 
the  most  important  ore,  from  which  we  obtain  mercury 
on  a  large  scale.  Small  globules  of  pure  mercury  are 
also  found  in  many  porous  stones. 

377.  Preparation  on  a  Large  Scale.  —  Experiment.  — 
Mix  a  little  vermilion  with  half  its  quantity  of  iron 
filings,  and  heat  the  mixture  in  a  dry  test-tube  ;  small 
globules  of  mercury  will  soon  deposit  themselves  on 
the  upper  cooler  portions  of  the  glass,  while  the  sul- 
phur remains  combined  with  the  iron.  Mercury  is  ob- 
tained in  a  similar  manner  from  native  cinnabar,  by 
distilling  it  with  iron  or  lirne  in  large  iron  retorts ;  the 
foreign  earths  remain  behind  in  the  latter.  This  heavy 
liquid  is  imported  either  in  leather  bags,  iron  flasks,  or 
hollowed  out  bamboo-canes. 

378.  Amalgams.  —  Experiment. —  Introduce  a  glob- 
ale  of  mercury  into  a  porcelain  dish,  put  upon  it  a 
piece  of  lead,  and  let  them  remain  for  some  time  in 
contact;  both  metals  will  intimately  combine  together. 
If  the  proportion  of  mercury  is  small,  a  friable  mass 
is  produced,  but  by  increasing  the  quantity,  a  paste, 
and,  if  still  more  is  added,  a  liquid  solution,  is  ob- 
tained. Mercury  will  combine  in  a  similar  manner 
with  most  of  the  metals,  forming  what  are  called  amal- 
gams. The  amalgam  of  tin  is  especially  important  for 
silvering  glass,  so  that  the  rays  of  light  falling  upon  the 
surface  of  the  glass  may  be  reflected  by  the  bright  coat- 
ing of  the  amalgam.  Such  glasses  are  called  mirrors. 


SILVER,  ARGENTUM  (Ag). 
At.  Wt.  =  1350.  —  Sp.  Gr.  =  10.5. 

379.   Silver  conveys  to  us  a  distinct  conception   of 
what  is  understood   by  a  noble  metal.     We  can  let  a 


SILVER. 

dollar  of  pure  silver  remain  exposed  to  the  a'r,  we  can 
throw  it  into  the  water,  or  bury  it  in  the  earth  ;  it  does 
not  rust.  We  can  subject  it  to  the  greatest  heat;  it 
may  perhaps  change  Its  form,  and  melt  (at  about 
1000°  C.),  but  it  does  not  oxidize  nor  volatilize.  Silver 
has  also  a  higher  value  than  most  other  metals,  not  only 
on  account  of  its  unchangeableness,  but  because  its  ores 
are  of  comparatively  rare  occurrence  in  nature,  and  the 
process  of  obtaining  them  is  more  costly  than  that  of 
other  ores.  A  pound  of  silver  is  worth  about  fifteen  dol- 
lars. It  is  principally  on  account  of  these  two  circum- 
stances that  silver  and  gold  have  been  made  to  serve  as 
the  medium  of  exchange  in  the  saff  and  purchase  of 
commodities, — that  they  are  used  as  money.  The  beau- 
tiful lustre  of  silver,  and  its  extraordinary  ductility,  have 
moreover  rendered  it  a  favorite  and  appropriate  metal 
for  various  articles  of  luxury,  and  for  plating  other 
metals.  The  old  name  for  silver  is  Luna  ( D  )• 

Alloys  of  Silver.  —  As  pure  silver  is  very  soft,  and 
would  quickly  wear  out  in  using,  it  is  generally  alloyed 
with  copper,  whereby  it  is  rendered  harder,  without 
losing  its  ductility.  If  the  proportion  of  copper  is  only 
one  fourth,  the  silver  still  retains  its  beautiful  white  col- 
or ;  but  if  more  copper  is  added,  the  alloy  becomes  yel- 
low, and  finally  red,  by  use.  It  has  been  agreed  to  call 
a  quantity  of  pure  silver,  weighing  8  ounces,  a  fine 
mark.  If  the  sample  is  an  alloy  of  silver  and  copper, 
the  question  is  always  asked,  What  is  the  proportion  of 
pure  silver  in  8  ounces  ?  If  it  amounts  to  7J  ounces, 
the  silver  is  said  to  be  7J  ounces  fine ;  if  6,  or  4,  or  2 
ounces  of  silver  are  contained  in  it,  it  is  understood  to 
be  6,  or  4,  or  2  ounces  fine.  Accordingly  silver  6  oun- 
ces fine  contains  three  fourths  of  silver  and  one  fourth 
of  copper,  from  which  plate  and  the  larger  coins,  for  in* 


394 


HEAVY    METALS. 


stance,  dollars,  are  made.*  In  the  two-ounce  silver,  on 
the  contrary,  the  proportions  are  one  fourth  of  silver 
and  three  fourths  of  copper ;  this  is  used  for  some  of  the 
smaller  modern  German  coins,  for  instance,  grosch  and 
half-grosch  pieces,  &c.  When  recently  stamped,  they 
are  yellow,  but  the  surface  of  them  is  rendered  white 
by  boiling  them  with  cream  of  tartar  and  water,  be- 
cause some  of  the  copper  is  thereby  dissolved,  and  con- 
sequently a  thin  coating  of  pure  silver  is  produced. 
By  due  weight  is  understood  the  weight  of  a  coin  ;  by. 
value,  the  fineness  of  the  silver  employed. 


Expt 


leriments  with  Silver. 

380.  In  order  to  oxidize  silver,  it  must  be  treated 
with  acids ;  it  dissolves  most  readily  in  nitric  acid.  In 
the  following  experiments,  care  must  be  taken  not  to 
touch  the  solution  of  silver  with  the  finger,  as  the  skin 
-s  stained  black  by  it. 

Nitrate  of  Oxide  of  Silver. —  Experiment.  —  Add  some 
nitric  acid  to  a  silver  coin  placed  in  a  beaker-glass, 
which  must  be  put  in  a  warm  place ;  if  after  a  few 
days  the  coin  is  not  entirely  dissolved,  add  more  nitric 
acid,  and  wait  till  the  solution  is  completed.  The  blue 
solution  consists  of  oxide  of  silver  and  of  oxide  of  cop- 
per, both  combined  with  nitric  acid. 

To  separate  these  two  metals  from  each  other,  put 
some  bright  copper  coins  into  the  solution,  and  set  it 
aside  in  a  warm  place  for  a  few  days,  occasionally  giv- 
ing it  a  circular  motion.  The  separated  laminae  are 
pure  silver,  which  are  to  be  digested  with  ammonia, 
until  this  ceases  to  be  colored  blue.  The  silver,  after 
being  washed  and  dried,  is  dissolved  for  the  second 

*  "  The  gold  and  silver  coins  [Federal  Money]  contain  nine  tenths  pure 
metal,  and  one  tenth  alloy." 


SILVER,  395 

time  in  nitric  acid,  and  the  liquid,  diluted  with  water,  is 
kept  as  solution  of  silver. 

Lunar  Caustic.  —  By  evaporating  this  solution,  nitrate 
of  oxide  of  silver  ( Ag  O,  N  OJ  is  obtained,  in  white  tab- 
ular crystals.  When  these  are  fused  and  formed  into 
slender  sticks  \y  casting  in  brass  moulds,  they  consti- 
tute lunar  caustic,  known  as  a  corrosive  agent,  em- 
ployed for  removing  proud-flesh,  warts,  &c.  (fused  ni- 
trate of  silver).  It  not  only  attacks  the  texture  of  the 
skin  and  dyes  it  black,  but  also  other  organic  sub- 
stances; on  account  of  this  property,  it  is  often  em- 
ployed for  dyeing  black  the  hair,  an£  also  bones  and 
ivory,  as  in  chess-men,  &c.  The  black  color  proceeds 
from  the  separation  of  the  oxide  of  silver.  Nitrate  of 
silver  forms  also  the  indelible  ink  used  for  writing  on 
linen. 

381.  Experiments  with  Nitrate  of  Silver. 

Experiment  a.  —  Place  a  small  piece  of  lunar  caustic 
upon  charcoal,  and  heat  it  before  the  blow-pipe ;  it  de- 
flagrates and  yields  metallic  silver,  which  may  be  easily 
fused  at  a  stronger  heat. 

Experiment  b.  —  ^dd  some  ammonia  to  a  solution  of 
lunar  caustic;  the  dark-gray  precipitate  is  oxide  of  sifter 
(AgO).  If  more  ammonia  is  added,  it  is  redissolved. 
It  would  be  dangerous  to  continue  this  experiment  any 
further,  as  the  oxide  of  silver  combines  with  ammonia 
and  f 3rms  fulminating'  silver,  which  explodes  violently 
on  percussion  or  friction.  Another  explosive  compound 
may  be  prepared  by  uniting  the  oxide  of  silver  with  ful- 
minic  acid. 

Experiment  c.  —  Chloride  of  Silver.  —  Dilute  with  wa- 
ter part  of  the  solution  of  silver  obtained  in  §  380,  and 
add  to  it  muriatic  acid,  or  a  solution  of  common  salt 


396  HEAVY    METALS. 

you  obtain  a  white  curdy  precipitate  of  chloride  of  silver 
(Ag  Cl).  This  precipitate  is  so  insoluble  in  water,  that 
it  will  impart  a  cloudiness  to  a  solution  of  silver  diluted 
a  millionfold  (§  187) ;  it  is,  however,  easily  dissolved 
by  ammonia  (test  of  salts  of  silver).  This  relation  of 
the  solution  of  silver  to  common  salt  is  made  use  of 
by  silversmiths  for  testing  silver  alloyed  with  copper, 
as  the  quantity  of  pure  silver  in  the  alloy  may  be  esti- 
mated from  the  amount  of  the  solution  of  salt  required 
for  its  complete  precipitation  (humid  assay  of  silver). 
Chloride  of  silver  is  also  called  horn-silver,  having  for- 
merly received  this  name  from  the  horn-like  appearance 
it  assumes  on  melting. 

Experiment  d.  —  After  having  decanted  the  superna- 
tant liquid,  rub  the  chloride  of  silver  with  a  cork  upon 
a  sheet  of  paper,  and  let  it  dry  in  a  dark  place,  —  in  a 
drawer,  for  instance ;  it  remains  white.  Now  inclose 
the  sheet  in  a  book,  so  that  one  half  may  be  exposed  to 
the  light ;  this  part  soon  acquires  a  violet,  and  finally  a 
black  color,  while  that  protected  from  the  light  remains 
white.  Thus  light  alone  is  capable  of  destroying  the 
affinity  between  silver  and  chlorine;  the  chlorine  es- 
capes, but  the  silver  remains,  and  in  this  state  of  fine 
subdivision  its  color  is  black.  On  this  action  of  the  so- 
lar light  on  certain  substances  were  founded  the  experi- 
ments made  some  years  since  by  the  natural  philoso- 
pher Daguerre,  who  at  length  succeeded  in  making  use 
of  the  sun  as  delineator,  and  of  the  salts  of  silver  (espe- 
cially the  compounds  of  silver  with  chlorine,  bromine, 
and  iodine)  as  crayons  or  India  ink,  in  producing  the 
so-called  Daguerreotype  or  photographic  impressions. 

Experiment  e.  —  Sulphur et  of  silver.  —  If  you  add  sul- 
phuretted hydrogen  to  a  solution  of  silver  you  obtain 
a  black  precipitate  of  sulphur  et  of  silver  (Ag  S).  This 


SILVER. 

compound  occurs  in  nature  as  the  most  important  sil- 
ver ore ;  it  is  called  silver-glance.  Silver  is  likewise 
found  in  a  pure  state,  or  in  combination  with  arsenic 
and  antimony,  as  red  silver  ore. 

382.  Preparation  of  Silver  an  a  Large  Scale.  —  The 
preparation  of  silver  from  its  ores  is  adapted  to  the  oth- 
er ores  with  which  the  silver  ores  are  commonly  mixed. 
The  three  following  methods  are  those  most  frequently 
resorted  to. 

a.)  Cupellation.  —  Galena  generally  contains  small 
quantities  of  silver.  In  order  to  extract  this,  the  galena 
is  first  reduced,  by  roasting  and  smelting  with  charcoal, 
to  metallic  lead,  in  which  the  silver  is  also  contained. 
This  mass,  containing  silver,  is  then  put  into  a  kind  of 
reverberatory  furnace,  called  the  refining  hearth,  and 
which  is  hollowed  out  like  a  kettle ;  it  is  there  heated 
for  a  day,  while  a  constant  current  of  air  is  passed  over 
the  metal,  until  all  the  lead  is  at  last  converted  into  ox- 
ide. The  oxide  of  lead  melts  in  the  heat,  and  flows  off 
partly  as  litharge  through  a  tube,  and  partly  soaks  into 
the  porous  mixture  of  clay  and  lime,  which  has  been 
firmly  beaten  down  on  the  hearth  of  the  furnace ;  but 
the  silver,  which  is  not  oxidized,  remains  behind  in  a 
metallic  state  (refined  silver).  This  is  rendered  still 
purer  by  being  again  fused  in  clay-basins  (smaller  cu- 
pels), which  absorb  the  remainder  of  the  litharge  (fine 
silver).  If  other  less  noble  metals  are  present  in  the 
silver  ore,  they  are  likewise  oxidized  and  carried  down 
into  the  cupel  by  the  litharge.  These  methods  can 
also  be  employed  on  a  small  scale  for  estimating  the 
alloys  of  silver  (assay  by  the  cupel). 

b.)  Liquation  Process.  —  Many  of  the  copper  ores  also 
contain  silver,  and  yield,  on  redaction,  a  copper  con- 
taining silver  (§  363).  The  silver  is  fused  and  extracted 
34 


398  HEAVY    METALS. 

from  this  ore  by  means  of  lead,  in  the  same  way  as 
potassa  is  dissolved  and  extracted  from  wood-ashes  by 
water.  The  calcined  ore  is  mixed  with  a  large  propor- 
tion of  lead,  and  then  fused  and  run  into  pigs,  called 
liquation-cake  S,  which  are  placed,  with  layers  of  char- 
coal, upon  an  inclined  hearth.  When  the  coal  is  ignited, 
the  heat  is  indeed  sufficient  to  melt  the  lead,  but  not 
the  copper ;  consequently  the  lead  flows  off,  and  carries 
with  it  the  silver,  whilst  the  copper  remains  behind. 
This  mixture  of  lead  and  silver  is  finally,  as  described 
at  a,  converted  into  metallic  silver  and  oxide  of  lead 
in  the  refining-hearth. 

c.)  Process  of  Amalgamation.  —  Silver  is  often  ex- 
tracted by  means  of  mercury  from  the  ores  containing 
pure  silver  or  sulphuret  of  silver,  but  no  admixture  of 
lead.  But  in  the  case  of  silver-glance  the  metallic  sil- 
ver must  first  be  separated  from  the  sulphur.  This  is 
done  by  two  operations.  In  the  first,  the  stamped  ore 
is  roasted  with  common  salt,  by  which  process  chloride 
of  silver  and  sulphate  of  soda  are  formed  ;  in  the  second, 
the  roasted  ore  is  mixed  with  water,  iron,  and  mercury, 
and  kept  in  constant  agitation  for  some  time  in  closed 
casks.  Chloride  of  iron  and  metallic  silver  are  thereby 
formed,  the  latter  of  which  is  dissolved  in  the  mercury. 
The  excess  of  mercury  is  then  filtered  off,  and  a  solid 
silver  amalgam  is  obtained  by  subjecting  it  to  pressure, 
and  the  mercury  is  at  last  completely  removed  from 
the  amalgam  by  distillation. 

GOLD,  AURUM  (An). 
At.  Wt.  =  2458.—  Sp.  Gr.  =  19.2. 

383.  Though  gold  is  found  in  most  countries,  yet  it 
is  disseminated  so  sparingly,  and  the  separation  of  it 


GOLD.  399 

from  the  rocks  or  the  river-sand  in  which  traces  of  it 
occur  is  attended  with  so  much  labor,  that  it  is  r^i- 
dered  the  most  costly  of  our  metals.  The  value  of 
gold  is  about  fifteen  times  greater  than  that  of  silver.* 
Its  unchangeableness,  its  beautiful  color,  its  high  lus- 
tre, and  grealt  density,  have  stamped  it  as  the  noblest 
metal,  -—  the  king  of  metals.  It  was  formerly  regarded 
as  the  symbol  for  the  king  of  the  stars,  and  was  called 
Sol,  or  Sun  (Q).  It  surpasses  even  silver  in  ductility, 
ma)  be  beaten  out  into  extremely  thin  leaves  (gold- 
leaf),  and  a  single  grain  of  gold  may  be  drawn  out 
into  a  wire  five  hundred  feet  in  length.  As  it  always 
exists  in  a  metallic  state  in  nature,  and  has  a  very 
great  specific  weight,  the  most  simple  method  of  sep- 
arating it  from  the  sands,  or  from  the  stamped  ores,  is 
either  by  washing  with  water  or  by  amalgamation 
with  mercury. 

Pure  gold,  like  pure  silver,  is  exceedingly  soft,  and 
quickly  wears  out  in  using;  therefore,  when  it  is  to 
be  manufactured  into  coins  or  articles  of  luxury,  it  is 
alloyed  with  other  metals,  usually  silver  and  copper,  to 
render  it  harder.  The  quantity  of  pure  gold  contained 
in  a  mass  is  expressed  by  the  word  carat,  the  standard 
number  not  being  8,  as  in  silver,  but  24.  A  mark  oi 
gold  (8  ounces)  is  divided  into  24  parts  or  carats.  If 
gold  is  said  to  be  18  carats  fine,  it  is  understood  that  the 
mass  consists  of  three  fourths  (18  parts)  of  gold,  and  one 
fourth  (6  parts)  of  alloy ;  if  6  carats  fine,  of  one  fourth  (6 
parts)  of  gold,  and  three  fourths  (18  parts)  of  alloy,  &c. 

384,  Parting  of  Gold.  —  In  order  to  obtain  fine  gold 
from  alloyed  gold,  or  to  separate  it  from  silver  con- 

*  "  Gold  is  regularly  purchased  by  the  Bank  of  England  at  the  rate  ot 
£3  17s.  9d ,  and  issued  at  the  rate  of  £  3  17s.  lO^d.  per  ounce  of  22  carats 
! eleven  twelfths)  fine."  — Waterston's  Cyclopedia,  of  Commerce 


400  HEAVY     METALS 

taining  gold,  it  is  boiled  with  concentrated  sulphuric 
acid,  which  must  be  done  in  iron  kettles ;  the  concen- 
ffated  sulphuric  acid  does  not  dissolve  iron.  The  sil- 
ver and  copper  are  dissolved  with  the  formation  of  sul- 
phurous acid,  while  the  gold  remains  behind  undis- 
solved,  as  a  brown  powder.  From  the  solution  of  silvei 
and  copper,  the  silver  is  precipitated  by  copper,  and 
blue  vitriol  is  obtained  as  a  secondary  product.  This 
operation  is  called  refining'. 

Formerly,  with  the  same  view,  silver  containing  gold 
was  dissolved  in  nitric  acid>  which  does  not  dissolve  the 
gold,  though  it  does  silver.  In  this  case  the  remark- 
able fact  was  observed,  that  the  silver  was  completely 
dissolved  only  when  three  fourths  of  silver  were  present 
to  one  fourth  of  gold  (two  thirds  of  silver,  however,  is 
an  adequate  proportion) ;  hence  the  term  quartation. 
If  more  than  one  fourth  or  one  third  of  gold  is  contained 
in  the  alloy,  the  gold  exerts  a  protecting  influence  upon 
the  silver,  so  that  the  latter  is  not  attacked  and  dis- 
solved by  the  nitric  acid. 

The  most  simple  mode  of  testing  gold  is  to  rub  some 
of  it  off  upon  a  black  flint  slate  (touchstone),  and  ap- 
ply to  the  mark  a  drop  of  aqua-fortis.  If  the  gold  is 
pure  the  yellow  stroke  remains  unchanged,  but  if  al- 
loyed it  partly  disappears;  if  it  is  only  an  imitation 
of  gold,  for  instance,  tombac,  it  entirely  dissolves. 

385.  Gold  and  Acids.  —  None  of  the  common  acids 
alone  can  dissolve  gold,  since  this  metal  is  in  a  high 
degree  indifferent  towards  oxygen  and  acids.  Chlorine 
is  the  only  means  of  rendering  it  soluble  (§  152). 
Commonly  the  chlorine  is  obtained  for  this  purpose  by 
mixing  muriatic  with  nitric  acid  ;  in  this  mixture,  the 
well-known  aqua  regia,  the  gold  dissolves  completely 
by  sufficient  heating,  and  a  brownish-yellow  liquid  is 


GOLD.  401 

obtained  (solution  of  gold).  By  evaporating  this  solu- 
tion to  dryness,  terchloride  of  gold  (Au  C13)  is  ob- 
tained, as  a  brownish-red  deliquescent  salt.  Metallic 
gold  separates  from  it  on  exposure  to  the  light,  and  like- 
wise separates  by  introducing  phosphorus,  iron,  zinc, 
and  other  metals,  into  a  solution  of  it. 

Experiments  with  Gold. 

386.  Gilding-.  —  Experiment  a.  —  Dip  a  dry  test-tube 
into  a  diluted  solution  of  gold,  so  as  to  moisten  the  bot- 
tom of  it,  and  then  heat  it  over  the  flame  of  a  spirit- 
lamp  ;  it  will  become  gilded,  —  a  proof  that  gold  has 
only  a  very  feeble  affinity  for  chlorine,  since  it  releases 
it  at  a  mere  gentle  heat. 

Experiment  b.  —  Drop  some  of  the  solution  of  gold 
upon  blotting-paper  ;  let  the  paper  dry,  and  then  hold 
it  by  means  of  a  wire  over  the  flame  of  a  spirit-lamp ; 
you  obtain  finely-divided  gold,  mixed  with  the  ashes  of 
the  paper  as  a  coherent  loose  mass.  If  you  rub  this  for 
some  time  upon  a  bright  silver  spoon,  with  a  soft 
cork  which  has  been  dipped  in  salt  water,  the  silver  be- 
comes gilt  (cold  gilding').  There  are  other  methods  of 
gilding ;  —  the  moist  gilding,  in  which  the  copper,  brass, 
or  silver  articles  are  boiled  with  a  very  diluted  solution 
of  gold,  to  which  some  bicarbonate  of  soda,  or  cyanide 
of  potassium,  has  been  added ;  the  hot  or  quicksilver 
gilding,  by  which  these  articles  are  smeared  with  a  so- 
lution in  mercury,  and  afterwards  heated ;  the  galvanic 
gilding,  which  is  done  in  the  same  manner  as  the  gal- 
vanic coppering.  The  silvering  of  metals  is  conducted 
on  the  same  principle. 

387.  Gold  Powder.  —  Experiment.  —  Drop    into    a 
weak  solution  of  sulphate  of  iron  some  muriatic  acid, 
and  then  some  of  the  solution  of  gold ;  the  liquid  im- 

34* 


402  HEAVY    METALS. 

mediately  assumes  a  changeable  dark  and  brownish 
color,  but  it  appears  of  a  beautiful  blue  color  by  trans- 
mitted light.  On  standing,  a  brown  substance  is  de- 
posited, which  is  gold  in  the  state  of  minutest  subdi- 
vision (gold  powder).  The  green  vitriol  is  at  the  same 
time  converted  into  the  sulphate  of  the  sesquioxide  of 
iron,  and  into  sesquichloride  of  iron  ;  decomposition  is 
thus  produced,  by  the  great  tendency  of  the  protoxide 
of  iron  to  pass  over  into  the  sesquioxide  of  iron.  In 
this  way  the  workers  in  gold  precipitate  that  metal  from 
liquids  containing  it.  By  triturating  gold  powder  with 
oil  of  lavender,  the  color  made  use  of  by  painters  for 
gilding  porcelain,  glass,  &c.,  is  obtained. 

388.  Gold  and  Oxygen.  —  If  the  solution  of  gold  is 
applied  to  the  skin,  or  to  any  other  organic  substance, 
it  imparts  to  it  on  drying  a  dark  purple-colored  stain, 
proceeding  from  the  protoxide  of  gold  (Au  O).     This 
protoxide  of  gold  is  also  formed  on  the  addition  of  the 
solution  of  gold  to  protochloride  of  tin  (purple  of  Gas- 
sius).    That  the  most  beautiful  purple  color  is  produced 
by  this  on  glass  and  porcelain  has  already  been  men- 
tioned, under  the  head  of  tin  (§  322).     Gold  may  be 
recognized  in  its  solutions  by  salt  of  tin.      Teroxide 
of  gold  (Au  O3)  is  of  a  brownish-black  color,  and  com- 
ports itself  like  an  acid  towards  bases.     It  combines 
with  ammonia,  like  the  oxide  of  silver,  forming  fulmi- 
nating gold. 

389.  Sulphuret  of  Gold.  —  When  sulphuretted  hydro- 
gen is  added  to  a  solution  of  gold,  a  black  precipitate 
of  sulphur et  of  gold  is  produced,  which  is  soluble  in  sul- 
phuret  of  ammonium.     Gold  cannot  be  united  directly 
with  sulphur,  by  fusing  them  together. 


PLATINUM.  403 

PLATINUM  (Ft). 
At.  Wt.  =  1232.  — Sp.  Gr.  ==  21.5. 

390.  Platinum,  a  metal  of  still  greater  density  than 
gold,  was  brought  in  the  last  century  from   America, 
where  it  was  found,   in   the  form  of  small,  flattened 
grains,  mixed  with  the  sands  from  which  the  gold  was 
washed.     It  received  the  name  platinum,  derived  from 
the  Spanish  word  plata,  silver,  on  account  of  its  re- 
semblance to  silver   in   color   and    ductility.     It   was 
afterwards  found  also  in  the  sand  of  the  Ural  Moun- 
tains, in  compact  lumps,  from  the  size  of  a  flax-seed  to 
that  of  a  man's  fist.    Platinum,  like  gold,  is  a  noble  met- 
al, and,  like  iron,  is  tenacious,  ductile,  and  can  be  welded, 
and  is,  moreover,   infusible    at   the    strongest   furnace 
heat.     These  properties  have  rendered  platinum  an  in- 
valuable metal  to  the  chemist.     Sulphuric  and  hydro- 
fluoric acids  can  be  distilled  in  platinum  retorts,  aqua- 
fortis can  be  boiled  in  platinum  capsules,  and  substances 
can  be  subjected  to  the  strongest  white  heat  in  plati- 
num crucibles,  or  on  platinum  foil  or  wire,  without  the 
platinum  articles  being  broken  or  melted.     It  is  only 
necessary  to  be  careful  that  no  metal  be  heated  with 
platinum,  as  a  fusible  alloy  might  thus  be  formed,  and 
the  platinum  apparatus  be  melted  or  broken  even  at  a 
moderate  heat.     The  value  of  platinum  is  intermediate 
between  that  of  gold  and  silver,  and  in  Russia  it  has 
been  coined  into  money.     It  is  less  adapted  for  articles 
of  luxury  than  either  of  these  two  metals,  its  color  not 
being  of  a  pure,  but  of  a  grayish  white,  and  its  lustre 
far  inferior  to  that  of  silver.     It  can  be  fused  by  the  oxy- 
hydrogen  blow-pipe,  or  by  the  galvanic  battery. 

391.  Platinum,  like  gold,  is  dissolved  by  heating  it 
for  a  long  time  with  aqua-regia;  and  a  dark-brown  so- 


104  HEAVY    METALS. 

lution  of  chloride  of  platinum  =  Ft  C12  is  obtained 
(solution  of  platinum).  A  small  quantity  of  this  solu- 
tion can  easily  be  prepared  from  one  or  several  pieces 
of  spongy  platinum,  such  as  are  employed  in  the  Do- 
bereiner  hydrogen-lamp. 

Experiments  with  Platinum. 

392.  Finely  divided  Platinum.  —  Experiment. —  Add 
a  few  drops  of  a  solution  of  platinum  to  a  solution  of  sal 
ammoniac  ;  the  two  salts  will  combine  together,  forming 
a  yellow  insoluble  double  salt,  which  is  called  chloride 
of  platinum  and  ammonium.  After  settling,  decant  the 
supernatant  liquid ;  let  the  precipitate  partly  dry  in  a 
dish,  so  that  it  forms  a  moist  paste ;  affix  it  to  a  plati- 
num wire,  several  times  bent,  and  hold  it  in  the  flame 
of  a  spirit-lamp.  The  sal  ammoniac  flies  off,  but  the 
platinum  remains  behind  as  a  gray,  loosely  coherent, 
porous  mass,  the  so-called  spongy  platinum.  When 
held  in  hydrogen,  it  becomes  red-hot,  and  inflames  the 
gas  (§  85).  The  porous  platinum  acts  on  gases  in  the 
same  manner  as  the  pump  of  an  air-gun,  only  far  more 
rapidly  and  vigorously  ;  it  absorbs  them,  and  condenses 
them  so  powerfully  together  into  its  pores,  that  the 
atoms  of  two  different  gases  often  approach  each  other 
sufficiently  near  to  combine  together  chemically.  As 
hydrogen  and  oxygen  are  in  this  instance  compelled  to 
unite,  so  the  spongy  platinum  can  force  many  other 
gases,  which  will  not  directly  combine  with  each  other, 
to  enter  into  combination. 

Pure  platinum  is  commonly  prepared  from  spongy 
platinum,  which  is  heated  to  whiteness  and  then  quick- 
ly compressed  by  strong  pressure.  A  compact  mass  is 
thus  obtained,  which,  on  being  again  heated,  may  be 
hammered  out  into  uniform  pieces,  and  afterwards 


PLATINUM.  40£ 

rolled  into  plates,  drawn  out  into  wire,  or  moulded  inta 
crucibles,  capsules,  &c. 

By  proper  chemical  means,  platinum  may  €k  divided 
still  more  minutely  than  in  the  case  of  spongy  plati- 
num ;  it  is  then  obtained  in  the  form  of  a  delicate  black 
powder,  which  possesses,  in  a  still  higher  degree  than 
spongy  platinum,  the  power  of  condensing  gases  into 
its  pores  ;  it  is  called  platinum  black.  If  some  alcoho 
be  dropped  upon  this  platinum  black,  ignition  takes 
place,  with  an  almost  instantaneous  conversion  of  the 
alcohol  into  acetic  acid.  The  reason  of  this  change  is 
to  be  sought  for  in  a  combination  of  the  alcohol  with 
the  oxygen  of  the  air,  which  is  effected  by  means  of  the 
porous  platinum  black. 

393.  Experiment.  —  If  you  perform  the  experiment 
described  in   §386  with   a  solution  of  platinum,  you 
obtain  a  coating  of  metallic  platinum  upon  the  glass. 
The  combination  between  this  metal  and  chlorine  is 
likewise  so  feeble,  that  heat  alone  is  able  to  destroy  it. 

394.  Experiment.  —  Dissolve  one  of  the  salts  of  po- 
tassa,  and  add  to  it  some  drops  of  solution  of  platinum ; 
here  also,  as  in  §  392,  a  yellow  insoluble  precipitate  is 
formed,  consisting,  of  potassium,  platinum,  and  chlorine. 
The  solution  of  platinum  serves,  therefore,  as  a  test  for 
the  salts  of  potassa  (and  salts  of  ammonia).     The  solu- 
tion of  platinum  is  precipitated  black  by  sulphuretted 
hydrogen  (sulphuret  of  platinum). 

Platinum  forms  with  oxygen  a  peroqfde  and  a  pro- 
toxide;  likewise  with  chlorine,  a  per  chloride  and  a  /??o 
\ochloride. 

Palladium,  Iridium,  Rhodium,  and  Osmium. 

395.  These  four  metals  are,  as  it  were,  the  satellites 
of  platinum ;  they  are  always  found  in  small  quantities 


406  HEAVY    METALS. 

in  the  crude  platinum  sand,  and  are  obtained  on  the 
purificatL^i  of  the  latter,  by  a  somewhat  elaborate  pro- 
cess. Tney  also  have  the  character  of  noble  metals. 


RETROSPECT    OF    THE    SECOND    GROUP    OF    THE 
HEAVY  METALS. 

1.  The  metals  lead,  bismuth,  copper,  mercury,  silver, 
gold,  and  platinum  do  not  possess  the  power  of  decom- 
posing water,  that  is,  of  abstracting  its  oxygen,  like 
the  metals  of  the  first  group ;  therefore,  concentrated 
acids  must  be  employed  for  their  solution. 

2.  Their  lowest  degrees  of  oxidation  are  bases,  while 
their  higher  degrees  comport  themselves  sometimes  like 
bases,  sometimes  like  acids. 

3.  These   metals   most   frequently  occur   in  nature 
uncombined,  or  as  sulphurets,  rarely  as  oxides. 

4.  They  have   a   greater   specific   weight  than   the 
metals  previously  described  ;  it  varies  from  8.8  to  21.5. 
(That  of  iridium  is  indeed  23.0). 

5.  They  are  all  precipitated  as  black  sulphurets  by 
sulphuretted   hydrogen   and   sulphide   of  ammonium ; 
the  sulphurets  of  gold  and  platinum  are  redissolved  by 
the  latter  reagent. 

6.  The  metals  mercury,  silver,  gold,  and  platinum, 
together  with  the  last-named   associates  of  platinum, 
are  called  noble  metals,  because  they  remain  bright  in 
the  air  or  in  \fl%ter.     When  oxidized  by  other  means, 
by  acids,  for  instance,  the  oxides  may  be  again  resolved 
merely  by  heat  into  metal  and  oxygen.     This  i?  efteited 
with  the  ignoble  metals  only  by  the  addition  of  9   '«• 
ducing  agent,  as  by  charcoal. 


CHROMIUM.  407 


THIKD  GROUP   OF  HEAVY  METALS. 

TUNGSTEN,    MOLYBDENUM,    TELLURIUM,    TITANIUM, 
TANTALUM,  VANADIUM,  NIOBIUM,  PELOPIUM. 

396.  These  metals  occur  only  as  chemical  rarities, 
and  have  not  yet  found  any  useful  application.     Their 
highest  degrees  of  oxidation  are  clearly  defined  acids. 
The  first  two  are  the  most  common,  as  they  are  some- 
times dug  out  from  tin  mines,  —  tungsten  as  wolfram 
ore,  and  molybdenum  as  sulphiiret  of  molybdenum,  or 
molybdate  of  lead. 

CHROMIUM  (Cr). 
At.  Wt.  =  328.  — Sp.  Gr.  =  6. 

397.  Chromium  has  only  been  known  within  a  few 
decades,  and  already  several  of  its  combinations  have 
become   common    and   valued   articles    of    commerce. 
The  cause  of  this  rapid  extension  is  owing  to  the  beau- 
tiful color  of  many  of  the  preparations  of  chromium,  on 
account  of  which  they  are  excellently  adapted  for  pig- 
ments.    This  also  has  given  rise  to  the  name  chromium 
(color). 

The  most  important  ore  of  chromium,  chromate  of 
iron,  an  insignificant  looking  black  mineral,  is  mostly 
obtained  in  North  America,  and  is  manufactured  into 
a  red  salt,  which  consists  of  potassa  and  chromic  acid. 
The  other  compounds  of  chromium  are  prepared  from 
this  salt. 

Fig.  159.  398.  The   Red   Chromate   or  Bichro- 

mate of  Potassa  (KO,  2  Cr  O3)  is  an 
acid  salt,  for  it  contains  two  atoms  of 
chromic  acid  and  one  atom  of  po- 
tassa, and  commonly  occurs  in  beau- 


408  HEAVY    MfcTALS. 

tiful  tabular  or  prismatic  crystals.  Rub  an  ounce  of  it 
with  ten  ounces  of  water ;  it  will  dissolve  in  it,  forming 
an  orange-yellow  solution. 

Experiment.  —  Add  to  one  half  of  this  solution  a 
dram  of  pure  carbonate  of  potassa,  and  concentrate  by 
evaporation  the  liquid,  which  has  become  of  a  cleat 
yellow  color;  on  cooling,  yellow  crystals  will  be  de- 
posited. These  consist  of  neutral  chromate  of  potassa 
(K  O,  Cr  O3).  The  potassa  of  the  carbonate  of  potassa 
has,  while  the  carbonic  acid  escaped,  combined  with 
the  second  atom  of  chromic  acid.  If  nitric  acid  is 
added  to  a  solution  of  the  yellow  salt,  the  liquid  be- 
comes darker,  and  on  evaporation  red  crystals  are  ob- 
tained, mixed  with  crystals  of  nitre.  It  is  obvious  that 
the  nitric  acid  has  abstracted  half  of  the  potassa. 

399.  Chromate  of  Oxide  of  Lead  (Pb  O,  Cr  O3).— 
Experiment.  —  Add  to  a  portion  of  the  solution  of  the 
*ed  salt  a  solution  of  sugar  of  lead,  as  long  as  there  is 
any  precipitate ;  this  precipitate,  when  washed  and 
•dried,  is  the  well-known  chrome  yellow,  and  is  the 
richest  and  most  vivid  of  all  the  yellow  pigments.  By 
mixing  it  with  white  substances,  —  for  instance,  chalk, 
talc,  clay,  gypsum,  &c.,  —  numerous  other  shades  of 
yellow  are  obtained,  as  new-imperial,  king's,  Paris,  &c., 
yellow  ;  but  by  mixing  it  with  Prussian  blue,  the  well- 
known  cheap  green  pigments  are  obtained,  called  olive 
green,  Naples  green,  green  cinnabar,  &c. 

Experiment.  —  If  chrome  yellow  is  stirred  up  with 
water  and  heated  with  some  carbonate  of  potassa,  it 
passes  into  chrome  orange,  which  is  also  used  as  a  paint- 
er's color.  This  contains  somewhat  less  chromic  acid 
than  the  chrome  yellow ;  accordingly,  the  potassa  ab- 
stracts from  tl*  chrome  yellow  a  portion  of  the  chromic 
acid,  which  is  rendered  apparent  by  the  yellow  color  of 
the  liquid  filtered  off  from  the  chrome  orange. 


CHROMIUM.  409 

By  fusing  with  riitre,  still  more,  even  a  half,  cf  the 
chromic  acid  may  be  withdrawn  from  the  chrome  yel- 
low ;  in  this  way  we  obtain  a  beautiful  red  color,  al- 
most rivalling  that  of  cinnabar,  chrome  red^  or  basic 
chromate  of  oxide  of  lead  (2  Pb  O,  Cr  Oa).  Thus  we 
see  that  the  colors  of  the  combinations  of  lead  comport 
themselves  inversely  to  those  of  the  combinations  of 
potassa ;  the  chrome  yellow  passes  into  orange  and  red 
by  abstracting  chromic  acid,  while  yellow  chromate  of 
potassa,  on  the  contrary,  becomes  red  by  adding  more 
chromic  acid,  or,  what  amounts  to  the  same,  by  with- 
drawing potassa. 

Experiment.  —  Chrome  yellow  has  obtained  also  a 
very  important  application  in  the  dyeing  and  printing 
of  yarns  and  fabrics.  First  dip  a  piece  of  cotton  into 
a  solution  of  chromate  of  potassa,  then,  after  it  has  be- 
come dry,  into  a  solution  of  sugar  of  lead ;  it  is  dyed 
yellow.  If  you  now  boil  a  little  quicklime  with  water 
in  a  vessel,  and  then  dip  the  cotton  dyed  yellow  into  it 
for  a  few  moments,  it  will  acquire  a  reddish-yellow  col- 
or, because  the  lime,  just  like  the  carbonate  of  potassa, 
abstracts  some  chromic  acid  from  the  chrome  yellow. 
It  is  scarcely  necessary  to  explain  any  further  why 
chrome  yellow  cannot  be  used  for  painting  the  walls  of 
apartments.  Salts  of  zinc  and  baryta  are  precipitated 
yellow,  salts  of  suboxide  of  mercury  a  brick-red,  and 
salts  of  silver  a  purple-red,  by  chromate  of  potassa. 

400.  Sesquioxide  of  Chromium  (Cr.^  O0).  —  Experiment. 
—  Boil  some  chrome  yellow  in  a  test-tube  with  muriatic 
acid;  it  becomes  \vhite,  and  the  liquid  green;  the  white 
residue  consists  of  muriate  of  oxide  of  lead  (chloride  of 
lead),  but  the  liquid  holds  in  solution  muriate  of  the 
sesquioxide  of  chromium  (sesquichloride  of  chromium). 
A  piece  of  moistened  litmus-paper,  or  of  paper  smeared 
35 


/110  HEAVY    METALS. 

with  ink,  introduced  into  the  tube  during  the  boiling,  is 
bleached,  as  chlorine  gas  escapes  at  the  same  time. 
The  process  is  analogous  to  that  of  the  evolution  of 
chlorine  from  black  oxide  of  manganese,  or  from  aqua- 
regia ;  the  chromic  acid  gives  up  half  its  oxygen,  and 
becomes  green  sesquioxide  of  chromium,  but  the  oxygen, 
becoming  free,  abstracts  from  a  portion  of  the  muriatic 
acid  its  hydrogen,  and  liberates  its  chlorine.  Decant 
the  green  solution,  dilute  it  with  water,  and  add  to  it 
ammonia;  the  ammonia  combines  with  the  muriatic 
acid,  and  the  sesquioxide  of  chromium  is  precipitated 
as  a  hydrate  having  a  bluish-green  color.  Dried  and 
ignited,  it  becomes  a  dark  green  anhydrous  oxide.  A 
fine  green  is  produced  by  it  on  porcelain  and  glass ;  ac- 
cordingly it  is  esteemed  as  a  valuable  vitrifiable  pig- 
ment. 

Experiment.  —  The  ease  with  which  chromic  acid 
gives  up  half  of  its  oxygen  may  also  be  shown  with 
chromate  of  potassa.  Dissolve  in  a  test-tube  a  few 
grains  of  red  chromate  of  potassa  in  warm  water ;  add 
a  few  drops  of  sulphuric  acid,  and  heat  the  solution 
stiU  more  strongly.  If  you  now  add  a  little  sugar  or 
some  drops  of  alcohol  to  it,  a  brisk  ebullition  ensues, 
and  the  color  of  the  solution  is  changed  from  red  to 
green;  sulphate  of  potassa  and  sulphate  of  sesqui- 
oxide of  chromium  are  now  contained  in  the  liquid. 

401.  Chromic  Acid  (Cr  O3). — Experiment.  —  Re- 
duce to  powder  half  an  ounce  of 

Fig.  160. 

red  chromate  of  potassa,  put  it  into 
a  porcelain  dish,  and  then  add  half 
an  ounce  of  water  and  half  an 
ounce  of  sulphuric  acid,  and  heat 
the  whole,  with  constant  stirring, 
for  five  minutes.  If  a  drop  of  it  is 


CHROMIUM.  411 

put  on  blotting-paper,  it  effervesces,  and  changes  its  yel- 
lowish-red color  to  green.  When  the  vessel  is  entirely 
cold,  add  an  ounce  of  cold  water  to  the  thick  saline 
mass,  stir  it  a  few  minutes,  and  then  carefully  decant 
the  liquid  into  a  beaker-glass.  What  remains  in  the 
dish  is  sulpliate  of  potassa;  but  we  have  in  the  liquid 
a  solution  of  chromic  acid,  which  is  precipitated  as  a 
red  mass  by  adding  to  it  from  one  and  a  half  to  two 
ounces  of  common  sulphuric  acid.  Cover  the  beaker- 
glass  with  a  small  board,  set  it  aside  for  twenty-four 
hours,  and  then  carefully  pour  off  the  supernatant  acid 
into  a  glass  vessel,  and  transfer  the  red  paste  remaining 
behind  to  a  new  brick,  by  which  the  fluid  portion  is 
completely  absorbed.  After  twenty-four  hours,  during 
which  time  the  precipitate  is  kept  covered  with  a  dish, 
you  obtain  the  chromic  acid,  as  a  crystalline,  red 
powder,  which  must  be  scraped  off  from  the  brick  with 
a  glass  rod,  and  put  into  a  wide-mouthed  phial,  provid- 
ed with  a  glass  stopper.  The  following  experiments 
will  illustrate  the  extreme  ease  with  which  this  highly 
interesting  body  decomposes  into  sesquioxide  of  chro- 
mium and  oxygen. 

Experiment  a.  —  Rinse  out  a  tumbler  with  strong 
alcohol,  then  throw  into  it  a  few  grains  of  chromic 
acid ;  the  alcohol  which  remains  adhering  to  the  tum- 
bler will  combine  with  half  the  oxygen  of  the  chromic 
acid,  with  such  energy,  that  it  ignites  and  instantane- 
ously bursts  into  flame.  The  change  which  the  alcohol 
has  hereby  undergone  is  at  once  revealed  by  the  odor, 
similar  to  that  of  the  vinegar  apartments;  in  the  latter, 
the  alcohol  contained  in  the  brandy,  beer,  &c.  slowly 
imbibes  oxygen  from  the  air,  and  is  converted  into 
vinegar;  hi  the  present  case  this  conversion  is  instan- 
taneously produced  by  the  oxygen  of  the  chromic  acid, 


412  HEAVY    METALS. 

Experiment  b.  —  Mix  in  a  small  mortar  as  much 
chromic  acid  as  can  be  taken  up  on  the  point  of  a 
knife  with  about  one  quarter  as  much  of  powdered 
camphor  (without  pressing  upon  it  strongly),  and  then 
let  some  drops  of  alcohol  fall  from  a  considerable  height 
into  the  mortar;  instantaneous  ignition  and  deflagra- 
tion ensue,  almost  as  if  you  were  burning  gunpow- 
der. The  residue  in  the  mortar  presents,  after  the 
decomposition,  the  appearance  of  an  elegant  green 
mossy  vegetation ;  it  consists  of  sesquioxide  of  chro- 
mium, which  at  the  moment  of  its  formation  was  scat- 
tered by  the  burning  camphor  fumes,  and  was  thereby 
most  delicately  subdivided. 

It  is  obvious  from  this  action,  that  chromic  acid  may 
be  classed  under  one  and  the  same  category  with  nitric 
acid,  chloric  acid,  manganic  acid,  hyperoxide  of  man- 
ganese, hyperoxide  of  lead  and  chlorine  (and  the  finely 
divided  platinum) ;  it  possesses  in  a  high  degree  the 
property  of  forcing  other  bodies  into  a  combination  with 
oxygen. 

ANTIMONY,  STIBIUM  (Sb). 
At.  Wt  =1613.  — Sp.  Gr.  =  6.7. 

402.  Antimony  has  a  lamellar  crystalline  texture,  and 
a  white  metallic  lustre,  like  bismuth,  but  without  the 
red  tint  of  the  latter  ;  it  far  exceeds  it  in  brittleness,  for 
it  may  be  easily  rubbed  to  powder  in  a  mortar.    The  so_- 
uble  preparations  of  antimony  are  undisguised  enemies 
to  animal  life,  and  consequently  the  stomach  exerts  it- 
self to  remove  from  the  body  all  such  compounds  intro- 
duced into  it.     This  is   effected  by  vomiting,  and  for 
the  very  reason  of  its  emetic  properties,  antimony  has 
oecorne  a  very  important  medicine. 

403.  Oxide  of  Antimony  (Sb  O3).  —  Experiment. — 


ANTIMONY.  413 

Antimony  does  not  alter  in  the  air,  but  if  a  piece  of  it 
is  heated  on  charcoal  before  the  blow-pipe,  it  soon 
melts,  and  burns  with  a  white  flame,  forming  an  oxide^ 
which  partly  escapes  as  a  white  vapor,  and  is  partly 
deposited  as  a  coating  on  the  charcoal.  If  you  let  the 
melted  metallic  globule  slowly  cool,  the  oxide  con- 
denses into  crystals,  which  form  afound  the  metal  an 
espalier  of  white  points.  When  thrown  into  a  paper 
capsule,  the  white  glowing  globule  will  burst  into  a 
multitude  of  small  spheroids,  which  skip  about  for  some 
time,  leaving  in  their  trail  a  pulverulent  oxide.  Anti- 
mony generally  contains  traces  of  arsenic;  hence  the 
smell,  like  that  of  garlic,  which  almost  always  accom- 
panies its  fusion. 

404.  Antimonic  Add  (Sb  O5). —  If  antimony  is  treat- 
ed with  nitric  acid,  it  takes  up  two  more  atoms  of  oxy- 
gen, and  becomes  antimonic  acid,  a  yellowish  powder, 
insoluble  in  water  and  acids.  At  a  glowing  heat  one 
atom  of  oxygen  is  expelled  from  this,  and  a  com- 
pound of  antimonic  acid  with  oxide  of  antimony  re- 
mains behind,  which  may  be  regarded  as  antimonious 
add  (Sb  O4).  It  is  not  volatile  at  a  glowing  heat,  and 
has  the  property  of  imparting  to  glass  and  porcelain  a 
yellow  and  orange  color. 

Experiment.  —  If  some  powdered  antimony  be  heated 
with  nitric  add,  the  same  thing  occurs  as  with  tin; 
namely,  the  metal  is  converted  into  a  white  powder, 
which  consists  of  a  mixture  of  both  degrees  of  oxida- 
tion, antimonic  acid  and  oxide  of  antimony.  A  similar 
orocess  takes  place  by  mixing  powdered  antimony  with 
nitre,  and  throwing  the  mixture  into  a  glowing  hot 
crucible;  in  this  case  only  antimonic  acid  is  formed, 
which  remains  behind  combined  with  the  potassa. 
The  antimoniate  of  potassa  may  be  dissolved  by  boiling 
35* 


414  HEAVY    METALS. 

in  water,  and  is  then  used  as  a  test  for  the  salts  of  soda, 
the  antimonic  acid  forming  with  the  soda  a  very  spar- 
ingly soluble  salt. 

405.  Chloride  of  Antimony.  —  Antimony  is  dissolved 
only  with  great  difficulty  by  muriatic  acid ;  a  solution 
is  more  readily  obtained  by  employing  sulphuret  of  an- 
timony instead  ofanetallic  antimony. 

Experiment.  —  Put  half  an  ounce  of  sulphuret  of  an- 
timony into  a  capacious  flask ;  pour  over  it  two  ounces 
and  a  half  of  muriatic  acid,  and  heat  it  in  a  sand- 
bath,  at  first  moderately,  but  afterwards  to  boiling  ;  the 
sulphuretted  hydrogen,  escaping  in  large  quantities,  is 
conducted  either  into  water  or  into  milk  of  lime,  by 
which  it  is  completely  absorbed.  The  sulphuret  of  an- 
timony and  the  muriatic  acid  are  converted  into  sul- 
phuretted hydrogen  and  chloride  of  antimony  (muriate 
of  oxide  of  antimony).  After  several  days'  repose,  de- 
cant the  clear  liquid ;  it  contains  chloride  of  antimony 
in  solution,  and  was  formerly  called  butter  of  antimony, 
By  continuously  rubbing  some  drops  of  it  upon  an 
iron  plate,  a  very  strongly  adhering  coating  of  oxide 
of  iron  is  produced,  which  imparts  to  the  iron  a  brown 
appearance,  and  renders  it  less  liable  to  rust.  In  this 
way  the  well-known  color  (browning)  is  given  to  gun- 
barrels. 

The  liquid  obtained  as  a  secondary  product,  filtered 
from  the  milk  of  lime,  is  to  be  regarded  as  hydrated 
sulphuret  of  calcium;  it  has  the  property  of  rendering 
hair  so  loose  in  the  skin,  that  it  may  easily  be  pulled 
tmt,  as  will  appear  if  a  piece  of  calf-skin  is  softened 
in  it  for  some  time. 

Experiment.  —  By  pouring  one  ounce  of  the  licuid 
muriate  of  antimony  into  ten  ounces  of  hot  water,  a 
decomposition  and  turbidness  are  produced,  as  in  the 


ANTIMONY.  415 

case  of  the  solution  of  bismuth ;  the  precipitate  is  ox- 
ide of  antimony  combined  with  a  little  muriatic  acid. 
Wash  it  several  times  with  water,  by  settling  and  de- 
canting the  liquid,  and  then  digest  it  for  an  hour  with 
a  solution  of  a  quarter  of  an  ounce  of  carbonate  of  soda 
in  two  ounces  of  hot  water,  whereby  the  muriatic  acid 
is  completely  removed.  The  precipitate,  being  again 
washed,  yields,  when  dry,  a  white  powder  of  oxide  of 
antimony.  The  same  preparation  is  thus  obtained  in 
a  moist  way,  as  by  igniting  the  metallic  antimony 
(§403). 

406.  Tartar  Emetic  (K  O,  T  +  Sb  O3  T  +  2  H  O).— 
Experiment.  —  Boil  in  a  porcelain  dish  two  ounces  oi 
distilled  water,  and  during  the  boiling  stir  in  a  mixture 
of  one  dram  of  oxide  of  antimdny,  and  one  dram  of 
cream  of  tartar.  When  the  liquid  is  half  boiled  away, 
filter  it  while  boiling,  and  pour  one  half  of  it  into  one 
ounce  of  strong  alcohol,  but  set  the  other  half  aside. 
In  both  cases  you  .obtain  a  white  salt,  tartar  emetic;  in 
the  latter  case  in  the  form  of  crystals,  but  in  the  former 
as  a  fine  powder,  because  tartar  emetic  is  insoluble  in 
alcohol,  and  consequently  is  precipitated  by  it  from  its 
solutions.  The  process  in  this  case  is  a  very  simple 
one.  Cream  of  tartar  is  an  acid  salt,  that  is,  a  combi- 
nation of  tartrate  of  potassa  with  free  tartaric  acid ;  this 
free  tartaric  acid  combines  with  the  oxide  of  antimojiy. 
Thus  we  obtain  tartrate  of  potassa  and  tartrate  of  ox- 
ide of  antimony,  which  unite  together,  forming  a  double 
salt,  tartar  emetic.  The  name  indicates  the  medicinal 
application  of  this  double  salt ;  it  is  the  most  usual 
means  of  inducing  vomiting.  One  grain  of  it,  dissolved 
in  half  an  ounce  of  Teneriffe  or  Sherry  wine,  forms  the 
well-known  wine  of  antimony.  One  ounce  of  tartar 
emetic  requires  fifteen  ounces  of  cold  water  for  so- 
lution. 


t416  HEAVY    METALS. 

407.  Sulpliuret  of  Antimony.  —  Experiment.  —  Ad£ 
some  sulphuretted  hydrogen  to  a  solution  of  tartai 
emetic  in  water :  an  orange-colored  precipitate  of  sul- 
phuret  of  antimony  (Sb  S3)  is  obtained,  which  becomes 
darker  on  drying.  Thus  the  combination  of  antimony 
may  be  very  well  recognized,  as  no  other  metal  yields 
a  sulphuret  of  thi^  color. 

We  most  frequently  find  antimony  in  nature  having 
this  composition  ;  but  the  native  sulphuret  of  antimony 
has  quite  another  color,  namely,  steel-gray,  and  in  other 
respects  likewise  a  very  different  exterior  condition,  as 
it  occurs  in  heavy  compact  masses,  which  on  the  frac- 
tured surface  appear  as  if  they  were  composed  of  small 
shining  needles  or  points.  On  account  of  this  appear- 
ance, it  has  received  the  name  of  prismatoidal  antimony 
glance.  It  melts  even  in  the  flame  of  a  candle,  and 
hence  may  be  obtained  from  the  different  sorts  of  rock 
with  which  it  is  associated,  merely  by  liquation.  When 
pulverized,  it  forms  a  black  gray  shining  powder,  which 
is  employed  by  the  farmer  as  a  familiar  remedy  in  the 
diseases  of  domestic  animals.  It  is  commonly,  but  er- 
roneously, called  antimony,  by  which  term  sulphuret  of 
antimony  is  implied. 

Experiment.  —  Boil  a  small  quantity  of  pulverized 
gray  sulphuret  of  antimony  with  a  solution  of  potassa, 
let  it  settle,  and  add  an  acid  to  the  decanted  liquid :  a 
brownish-red  precipitate  is  produced,  likewise  sulphuret 
of  antimony,  which  was  dissolved  by  the  potassa.  This 
sulphuret  of  antimony  (containing  an  oxide),  which  in 
th'e  apothecary's  shop  is  called  Kermes  mineral,  is  much 
more  finely  divided  (§  129)  than  the  gray,  and  thereby 
acquires  the  red  color ;  the  division  is  still  greater  in 
the  orange-colored  sulphuret,  prepared  from  the  tartar 
emetic. 


ARSENIC.  417 

These  three  combinations,  the  orange,  the  red,  and 
gray  sulphurets  of  antimony,  have  quite  a  similar  com- 
position ;  they  are  one  and  the  same  body,  only  existing 
in  different  isomeric  states. 

A  still  higher  sulphuret  of  antimony  (Sb  S5)  occurs  in 
the  pharmacopoeias,  under  the  name  of  the  golden  sul- 
phuret,  as  an  important  medicine  ;  it  h^s  an  orange  color, 
and  corresponds  in  its  constitution  to  antimonic  acid, 
as  the  gray  or  red  sulphuret  corresponds  to  the  oxide  of 
antimony. 

For  Antimoniuretted  Hydrogen,  see  §  418. 

408.  Preparation  of  Antimony.  —  In  order  to  sepa- 
rate metallic  antimony  from  the  sulphuret,  it  is  only  ne- 
cessary to  fuse  it  with  iron,  which  has  a  greater  affinity 
for  the  sulphur,  and  unites  with  it,  forming  sulphuret  of 
iron.     On  cooling,  the  heavy  metallic  antimony  settles 
at  the  very  bottom. 

409.  Alloys  of  Antimony.  —  Of  the  alloys  which  anti- 
mony forms  with  other  metals,  that  with  lead,  from 
which  types  are   cast,  deserves   especial   notice.     Lead 
alone  is  much  too  soft  to  be  employed  for  this  purpose, 
but  if  from  an  eighth   to  a  twelfth  part  of  antimony 
is  mixed  with  it,  it  acquires  such   a  degree  of  hard- 
ness, that  types  cast  from  it  may  be  used  for  printing 
many  thousand  times  without  losing  their  distinctness. 

ARSEXIC,  ARSENICUM  (As). 
At.  Wt.  =  937.  —  Sp.  Gr.  =  5.7. 

410.  Poisonous  as  arsenic,  is  almost  a  proverbial  ex- 
pression, and  it  shows,  in  this  respect,  at  least,  that  arse- 
nic is  well  known,  and  in  sufficiently  bad  repute.    In  fact, 
it  is  placed  among  the  metallic  poisons,  and  a  very  small 
quantity  of  it  produces  a  fatal  effect,  unless  antidotea 


41H  HEAVY    METALS. 

are  quickly  administered.  Happily,  in  recent  times  a 
means  has  been  discovered,  in  the  hydrated  sesqmoxide 
of  iron  (iron-rust),  by  which  most  of  the  combinations 
of  arsenic  may  be  rendered,  even  in  the  stomach,  insol- 
uble, and  thereby  harmless.  Before  this  remedy  and 
the  aid  of  the  physician  can  be  procured,  it  is  well  in 
cases  of  poisoning  by  arsenic,  as  in  cases  of  poison 
generally,  to  administer  milk,  white  of  eggs,  soap  suds, 
or  sugar.  On  account  of  the  dangerous  effects  of  arse- 
nic, the  greatest  care  must  be  taken,  in  experimenting 
with  it,  not  to  inhale  its  dust  or  vapor ;  the  vessels  that 
contain  it  must  also  be  most  carefully  washed,  and  the 
water  used  for  this  purpose  should  be  emptied  into  some 
place  not  accessible  to  domestic  animals. 

411.  Metallic  Arsenic.  —  Metallic  arsenic  is  not  unfre- 
quently  found  in  the  earth,  as  a  lead-gray  ore,  of  strong 
metallic  lustre.  The  artificially  prepared  metallic  arse- 
nic, which  soon  tarnishes  and  assumes  motley  colors  in 
the  air,  and  finally  falls  into  a  coarse  gray  powder,  is 
kept  on  hand  in  the  apothecaries'  shops,  under  the  name 
of  fly-poison.  If  boiled  with  water,  the  film  of  oxidized 
arsenic  dissolves,  and  a  very  poisonous  liquid  is  ob- 
tained (fly-poison).  A  fresh  film  of  oxide  is  produced 
upon  the  metal  which  remains,  and  thus  is  very  easily 
explained  why,  after  a  time,  a  new  poisonous  solution 
can  again  be  prepared  from  it,  without  any  perceptible 
decrease  of  the  original  powder. 

Fig.  i6i.  Experiment.  —  Put    a   piece 

of  arsenic  of  the  size  of  a  mil- 
let-seed into  a  glass  tube,  hold 
the  latter  by  one  end,  and  heat 
it;  the  arsenic  volatilizes  at 
180°  C.,  and  deposits  itself  on 
the  upper  portion  of  the  tube 


ARSENIC.  419 

as  a  brilliant  black  mirror ;  the  smell  of  garlic,  peculiar 
to  the  fumes  of  arsenic,  being  at  the  same  time  given 
off.  These  two  tests  are  employed  as  very  accurate 
for  detecting  the  presence  of  arsenic  in  other  bodies. 
Phosphorus,  when  exposed  to  the  air,  emits,  likewise, 
the  odor  o£^  garlic.  If  this  indicates  a  similarity  in 
these  two  bodies,  the  resemblance  is  rendered  still 
more  striking,  since  arsenic  behaves  very  much  like 
phosphorus  in  its  combinations  with  other  substances. 

412.   Wldte  Arsenic,  or  Arsenious  Acid  (As  O3). 

Experiment.  —  Let  the  arsenical  mirror  obtained  in 
the  above  experiment  be  heated  once  more,  but  in  an 
open  tube  ;  it  is  converted  into  a  vapor,  which  condense* 
on  the  colder  parts  of  the  tube,  partly  in  small  white 
crystals,  partly  as  powder.  Before  the  magnifying-glass 
these  crystals  appear  as  four-sided  double  pyramids 
(octahedrons) ;  their  constituent  parts  are  arsenic  and 
oxygen,  and  they  are  called  arsenious  acid,  ivhite  ar- 
senic, or  ratsbane.  When  arsenic  is  spoken  of  in  a 
popular  sense,  the  white  arsenic  is  always  implied.  It 
is  obtained  on  a  large  scale,  —  a.)  as  a  secondary  prod- 
uct in  the  roasting  of  tin,  silver,  and  cobalt  ores ;  b.) 
as  a  principal  product,  by  heating  arsenical  ores  with 
access  of  air  (in  the  arsenical  furnaces  in  Saxony  and 
Silesia).  In  both  cases  the  arseniojis  acid  passes  oft 
as  vapor,  with  the  smoke,  which  must  therefore  be 
conducted  through  long,  horizontal  chimneys,  till  it 
cools,  and  the  arsenious  acid  condenses  as  a  powder 
(ivhite  arsenic).  White  arsenic  is  often  re-sublimed  in 
some  appropriate  apparatus,  and  is  then  obtained  as 
amorphous  arsenious  acid,  in  solid  transparent  pieces. 
These  after  a  time  become  opaque  and  milk-white,  like 
porcelain,  without  changing  their  constitution  ;  another 


420  HEAVY    METALS. 

example  that,  even  in  solid  bodies,  atoms  can  alter  their 
relative  situations  (§  280). 

Arsenious  acid  is  especially  distinguished  from  the 
other  metallic  oxides  by  its  solubility  in  water,  which, 
indeed,  is  not  very  great,  since  one  grain  of  it  requires 
fifty  grains  of  cold  water,  or  from  ten  to  twelve  grains  of 
boiling  water,  for  solution ;  but  it  is  sufficiently  soluble 
to  render  these  solutions  exceedingly  dangerous  poisons. 
White  arsenic  is  -  generally  employed  for  killing  rats, 
moles,  and  other  troublesome  house  or  field  animals ; 
for  this  purpose  colored  arsenic  only  should  be  pur- 
chased, as  the  white  arsenic  looks  very  much  like  sugar 
or  flour,  and  might  easily  be  mistaken  for  it.  In  order 
to  prevent  its  being  carried  off,  it  is  best  to  strew  pow- 
dered arsenic  over  broiled  rinds  of  pork,  or  broiled  fish, 
nailed  upon  boards.  If  the  poison  is  put  in  stables, 
the  fodder-troughs  should  be  carefully  covered  over,  that 
the  poisoned  rats  may  not  vomit  the  poison  into  them. 

Arsenious  acid,  like  chloride  of  mercury,  prevents 
the  decay  of  organic  substances ;  therefore  the  skins  of 
animals  intended  for  shipping  are  rubbed  with  arsenic 
upon  the  flesh  side. 

Arsenious  acid  readily  gives  up  its  oxygen  in  the 
heat  to  other  bodies  ;  for  this  reason  it  is  added  by 
glass-makers  to  melted  glass,  to  convert  its  black  or 
green  color  into  yellow.  It  acts  like  black  oxide  of 
manganese  (§  297)  ;  namely,  it  oxidizes  the  protoxide 
jnto  sesquioxide  of  iron.  A  solution  of  wl;te  arsenic 
and  mercury  in  nitric  acid  is  used  by  hat-makers  to 
remove  the  shining  smooth  coating  from  the  fur  of 
hares. 

413.  Reduction  of  Wliite  Arsenic. 
Experiment.  —  Draw  out  a  glass  tube  into  a  point. 


ARSENIC.  421 

Fig.  its.  introduce  into  it  a  very  little  arsenious  acid,  and 
put  upon  it  a  splinter  of  charcoal;  then  heat  the 
tube  to  redness  in  the  flame  of  a  spirit-lamp, 
first  at  the  place  where  the  coal  lies,  and  after- 
wards at  the  pointed  extremity  of  the  tube ;  the 
glass,  becomes  coated  on  the  inside  above  the 
coal  with  a  black  metallic  mirror,  because  the 
oxygen  is  withdrawn  from  the  vapors  of  the 
arsenious  acid  while  they  pass  over  the  glow- 
ing coal.  This  is  one  of  the  surest  methods  of 
detecting  small  quantities  of  arsenic. 

414.   Combinations  of  WJiite  Arsenic  with  Bases. 

Experiment.  —  If  ten  grains  of  arsenious-  acid  and 
twenty  grains  of  carbonate  of  potassa  are  heated  with 
half  an  ounce  of  water,  the  arsenic  very  readily  dis- 
solves, and  a  solution  of  arsenite  of  potassa  is  obtained. 

a.)  Add  gradually  to  one  half  of  this  liquid  a  solution 
of  fifteen  grains  of  blue  vitriol  in  half  an  ounce  of  l;ot 
water;  a  yellowish-green  precipitate  soon  subsides, 
which,  on  drying,  passes  over  into  a  dark-green.  This 
arsenite  of  oxide  of  copper  occurs  in  commerce  under 
the  name  of  Scheele*s  green. 

b.)  The  other  half  of  the  solution  is  likwise  mixed  in 
a  flask  with  a  solution  of  fifteen  grains  of  blue  vitriol  in 
half  an  ounce  of  water,  and  then  acetic  acid  (concen- 
trated vinegar)  is  added  as  long  as  effervescence  con- 
tinues ;  the  whole  is  then  boiled  for  five  minutes,  after 
which  the  flask  is  put  in  a  basin  of  hot  water,  that  the 
cooling  may  take  place  very  slowly.  We  obtain  in  this 
way,  after  twenty-four  hours'  repose,  a  double  com- 
pound of  arsenite  and  acetate  of  copper,  which,  on  ac- 
count of  its  splendid  green  color,  is  extensively  used  as 
a  pigment.  Of  its  numerous  names,  those  most  known 
36 


423  HEAVY    METALS. 

are  Schweinfwth  green,  vert  de  mitis,  and  Vienna  green. 
This  color  is  as  poisonous  as  white  arsenic;  hence  ex- 
treme caution  in  the  use  of  it  cannot  be  too  strenu- 
ously urged ;  it  may  even  prove  dangerous  as  a  green 
paint  for  rooms,  since,  under  some  circumstances,  vola- 
tile combinations  of  arsenic  are  formed  from  it,  and 
unite  with  the  air. 

415.  Arsenic  Acid  (As  O5).  —  If  arsenious  acid  is 
boiled  with  nitric  acid,  it  takes  from  the  latter 
two  additional  atoms  of  oxygen,  and  becomes 
arsenic  acid.  The  same  acid  is  obtained,  com- 
bined with  potassa,  by  fusing  together  arseni- 
ous acid  and  nitre.  The  biarseniate  of  potassa 
thus  produced,  which  crystallizes  in  beautiful 
four-sided  prisms,  has  hitherto  been  consumed 
in  immense  quantities  in  calico-printing,  not  so 
much  to  produce  colors  as  to  prevent  their  formation 
on  certain  points  of  the  texture. 

•41(5.  Sulphur et  of  Arsenic.  —  Experiment.  —  Dissolve 
some  grains  of  arsenious  acid  in  boiling  water,  and  add 
to  the  solution  sulphuretted  hydrogen;  a  precipitate  of 
yellow  sulphur  et  of  arsenic  (As  S3)  is  formed,  three  at- 
"oms  of  sulphur  replacing  three  atoms  of  oxygen.  In 
this  way  arsenic  may  easily  be  detected  in  liquids,  and 
separated  from  them ;  the  salts  of  cadmium  and  oxide  of 
tin  are  the  only  ones,  except  arsenic,  which  give  a  yel- 
low precipitate  with  sulphuretted  hydrogen.*  Sulphuret 
of  arsenic  is  redissolved  by  sulphuret  of  ammonium. 

Sulphuret  of  arsenic  also  occurs  native,  and  is 
called  orpiment,  or  king's  yellow,  and  was  formerly 
used  as  a  yellow  pigment,  but  it  is  earnestly  advised 
never  to  employ  this  color  in  the  painting  of  rooms,  as 

*  Tne  salts  of  antimony  are  precipitated  of  an  orange-yellow  color  bj 
sulphuretted  hydrogen. 


ARSENIC.  423 

it  evolves  upon  lime  walls  an  exceedingly  poisonous 
gas  (arseniuretted  hydrogen).  A  sort  of  yellow  arsenic, 
having  the  color  of  yellow  wax  or  porcelain,  is  also  pre- 
pared in  arsenical  works  by  the  sublimation  of  white 
arsenic  with  a  little  sulphur;  this  consists  principally  of 
arsenious  a$id,  and  contains  but  a  small  quantity  of 
sulphuret  of  arsenic. 

A  combination  of  arsenic  with  one  atom  less  of  sul- 
phur (As  Sj,  which  is  sometimes  transparent  like  ruby- 
red  colored  glass,  and  sometimes  opaque  like-brownish- 
red  porcelain,  has  received  the  name  Realgar,  or  red  sul- 
phuret  of  arsenic. 

Preparation  of  Arsenic.  —  Arsenic  is  most  frequently 
found  combined  with  sulphur  and  iron,  as  arsenical  py- 
rites. Most  of  the  white  arsenic  is  prepared  from  this 
ore  by  roasting  it  in  a  reverberatory  furnace,  and,  as 
already  mentioned,  condensing  in  poison  towers  the 
fumes  containing  arsenious  acid.  The  iron  and  sulphur 
are  oxidized  at  the  same  time  with  the  arsenic;  but  the 
oxidized  iron  remains  behind,  and  the  oxidized  sulphur 
(S  O  )  escapes  with  the  smoke  into  the  air. 
417.  Arseniuretted  Hydrogen  Gas  (As  Hd). —  Exper- 
Fjo,  164  imSnt.  —  Introduce  into  a  small 

flask  diluted  sulphuric  acid  and 
some  pieces  of  zinc,  and  let 
the  hydrogen  which  is  evolved 
escape  through  a  tube  drawn 
out  to  a  point,  and  after  some 
time  ignite  it  (§  85) ;  you  ob- 
tain in  this  manner  a  hydrogen- 
lamp.  If  you  hold  a  glazed 
porcelain  capsule  for  some  min- 
utes in  the  flame,  you  will  per- 
ceive upon  it  only  a  circle  of 


424 


HEAVY     METALS. 


small  drops  of  water,  which  form  during  the  combustion 
of  the  hydrogen,  and  condense  on  the  cold  portion.  II 
you  now  dip  a  piece  of  wood  into  Schweinfurth  green, 
so  that  only  a  little  of  it  shall  remain  adhering  to  the 
wood,  and  introduce  it  into  the  flask,  the  flame,  after 
the  gas  has  been  rekindled,  will  present  a  bluish-white 
appearance,  and  will  deposit  on  the  porcelain  held  in  it 
a  black  or  brown  smooth  spot  (mirror)  ;  this  mirror  is 
metallic  arsenic.  Like  sulphur  and  phosphorus,  arse- 
nic also  will  combine  with  hydrogen,  forming  a  kind 
of  gas,  which,  in  company  with  the  free  hydrogen,  es- 
capes and  burns.  The  flame  is  cooled  by  a  cold  body 
below  the  temperature  which  arsenic  requires  for  burn- 
ing; hence  the  latter  condenses  on  the  porcelain,  just 
in  the  same  way  as  carbon  or  soot  is  deposited  on  it 
when  held  in  the  flame  of  a  candle.  The  carbon  sepa- 
rates as  a  light,  pulverulent  body,  arsenic  as  a  coherent 
mirror.  This  incredibly  sensitive  test  is  called,  after  its 
inventor,  Marsh's  arsenical  test.  It  follows  from  the 
previous  remarks,  that  care  should  be  taken  not  to  in- 
hale the  escaping  gas,  particularly  the  unburnt  gas;  but 
here  more  than  ordinary  caution  is  necessary,  as  arseni- 
uretted  hydrogen  is  a  most  poisonous  gas,  and  one  to 
which  some  chemists  have  already  fallen  a  sacrifice. 

418.  Antimoniuretted  Hydrogen.  —  Experiment.  —  Re- 
peat, the  same  experiment,  substituting  tartar  emetic  for 
Schweinfurth  green ;  black  spots  are  in  this  case  also 
deposited  on  the  porcelain,  but  they  are  darker,  and 
often  have  a  sooty  appearance ;  they  consist  of  metallic 
antimony.  To  distinguish  spots  of  antimony  with  cer- 
tainty from  spots  of  arsenic,  drop  upon  them  a  solution 
uf  chloride  of  lime ;  the  spots  of  antimony  remain  un- 
changed, while  the  arsenical  mirrors  dissolve  immedi- 
ately. 


RETROSPECT.  425 

Antimony  and  arsenic  are  the  only  metala  which 
combine  with  hydrogen;  they  comport  themselves  in 
this  respect  like  the  metalloids  ;  they  may  be  regarded 
as  the  link,  the  bridge,  which  joins  the  territory  of  the 
non-metallic  bodies  or  metalloids  with  the  metals. 

• 

RETROSPECT  OF  THE  THIRD  GROUP  OF  THE  HEAVY 
METALS. 

1.  The    metals    chromium,   antimony,  and    arsenic, 
together  with  the   previously-mentioned   rarer  metals, 
cannot  decompose  water  ;  therefore  concentrated  acids 
must  be  employed  for  their  solution. 

2.  Their  lower  degrees  of  oxidation  comport  them 
selves  sometimes  like  bases,  and  sometimes  like  acids, 
but  the  higher  only  as  acids. 

3.  These    metals    occur    most  frequently  in    nature 
combined  with  sulphur. 

4.  Antimony  and  arsenic  are  precipitated  from  their 
solutions  as  sulphurets  by  sulphuretted  hydrogen,  but 
are  redissolved  by  sulphuret  of  ammonium.     Chromi- 
um is  not  converted  into  a  sulphuret  by  sulphuretted 
hydrogen. 

5.  Antimony  and  arsenic  can,  like  the   metalloids, 
unite  \\&h  hydrogen,  forming  gaseous  compounds. 


RETROSPECT    OF    ALL    THE    METALS. 

Metals. 

1.  All  metals  have  a  peculiar  lustre,  are  opaque,  and 
the  best  conductors  of  heat  and  electricity. 

2.  Most   of  the   metals   will  crystallize  on   cooling 
slowly  (most  commonly  in  cubes). 

3.  All  the  metals  are  fusible,  but  at  very  different  de- 
grees of  heat  ;  many  of  them,  also,  may  be  volatilized. 

36* 


426 


HEAVY     METALS. 


4.  All  metals  can  combine  with  oxygen,  sulphur,  and 
chlorine, 

5.  They   likewise   combine  with   each   other    when 
they  are  fused  together  (alloys). 

Metallic  Oxides. 

6.  Most   of  the  metals  form  basic  oxides  with  oxy- 
gen.     Almost  all  the  metallic  oxides  are  insoluble  in 
water. 

7.  Many  metals  possess  one  known  degree  only  of 
oxidation,  but  most  of  them   have  two,  some,  indeed, 
three,  four,  and  even  five  degrees  of  oxidation.     The 
highest  comport  themselves  as  acids. 

8.  Metallic  oxides  may  be  prepared  from  the  metals : — 
a.)  By  exposure  to  the  moist  air. 

b.)  By  heating  with  access  of  air. 

c)  By  decomposition  of  water  at  the  ordinary 
temperature. 

d.)  By  decomposition  of  water  at  a  red  heat. 

e.)  By  decomposition  of  water  with  the  aid  of  an 
acid,  and  precipitation  by  a  strong  base. 

f.)  By  treating  with  concentrated  acids,  and  pre- 
cipitation by  a  strong  base. 

g1.)  By  heating  with  nitre  or  chlorate  of  potassa. 

9.  The  metallic    oxides   may  be   deoxidi&d  or  re- 
duced to  metals :  — 

a.)  By  mere  heating  (noble  metals). 

b.)  By  heating  with  charcoal. 

c.)  By  heating  in  hydrogen  gas. 

d.)  By  a  more   electro-positive   metal    (having  a 

greater  affinity  for  oxygen). 
e.)  By  the  galvanic  current. 


RETROSPECT.  42? 

Metallic    Sulphur ets. 

10.  The  sulphurets  of  the  light  metals  are  soluble  in 
water,  those  of  the  heavy  metals  are,  on  the  contrary, 
insoluble. 

11.  A  metalv  has  commonly  as  many  degrees  of  sul- 
phuration  as  of  oxidation. 

12.  The  metallic  sulphurets  may  be  prepared,  — 

a.)  Directly  by  rubbing  or  melting  together  sul- 
phur and  a  metal,  or  by  heating  the  metal  in  the 
fumes  of  sulphur. 

b.)  By  adding  sulphuretted  hydrogen  or  sulphuret 
of  ammonium  to  a  metallic  oxide  or  salt. 

c.)  By  heating  metallic  sulphates  with  charcoal. 

13.  Sulphur  may  be  expelled  from  the  metallic  sul- 
phurets, — 

a.)  By  heating  them  with  access  of  air  (roasting). 

b.)  By  a  more  electro-positive  metal. 

c)  By  heating  in  steam. 

d.)  By  heating  with  strong  acids. 

Metallic   Chlorides. 

14.  Most  of  the   metallic  chlorides  may  be  crystal- 
lized, and  are  soluble  in  water. 

15.  As  a  general  rule,  a  metal  combines  in  as  many 
proportions  with  chlorine  as  it  has  degrees  of  oxida- 
tion. 

16.  Metallic  chlorides  are  prepared,  — 

a.)  By  bringing  the  metals  or  metallic  oxides  into 

contact  with  chlorine. 
b.)  By  dissolving  metals  in  muriatic  acid. 
c.)  By  dissolving  metals  in  aqua-regia. 
d.)  By  double  elective  affinity,  on  mixing  metallic 

chlorides  with  oxygen  salts. 


428  HEAVY    METALS. 

17.  Chlorine  may  be  separated  from  the  metals,  — 
a.)  By  mere  heating  (the  noble  metals  only). 
b.)  By  heating  in  hydrogen  gas. 
c.)  By  a  more  electro-positive  metal. 
d.)  By  a  stronger  acid,  for  instance,  sulphuric  acid. 

The  Oxygen  Salts. 

18    Every  acid  usually  forms  a  salt  with  every  me- 
tallic base;  hence,  there  is  an  infinite  number  of  salts. 

19.  Suboxides  must  receive  oxygen  and  hyperoxides 
part  with  it  before  they  can  combine  with  acids. 

20.  Most  of  the  salts  may  be  crystallized,  sometimes 
with  and  sometimes  without  water  of  crystallization. 

21.  The  salts  behave  very  differently  towards  water  ; 
some  dissolve  in  it  very  easily,  others  with  difficulty, 
and  others  not  at  all. 

22.  Salts  may  be  prepared^  — 

a.)   By  exposing  metals  to  the  air. 

b.)   By  dissolving  them  or  their  oxides  in«acids. 

c.)  By  decomposition  of  the  metallic  sulphurets 
with  acids  ;  also  by  a  spontaneous  weathering 
of  the  metallic  sulphurets. 

d.)  By  mutual  decomposition  by  means  of  predis- 
posing simple  or  double  elective  affinity. 

23.  Many  of  the  salts,  by  mere  heating,  lose  their 
acids,  which  either  escape  (carbonic  acid),  or  burn  up 
(organic  acids). 

24.  The  salts,  like  the  oxides,  may  be  reduced  to  met* 
als.     If  this  is  effected   by  ignition  with  charcoal,  it  is 
necessary  to  superadd  a  strong  base  (carbonate  of  soda, 
lime),  which  attracts  the  acid  from  the  salt. 

Occurrence  of  Metals  in  Nature. 

25.  The  metals  principally  occur  native  in  five  forms, 


RETROSPECT  429 

viz.:  —  1.  uncombined,  or  massive',  2.  combined  with 
sulphur,  as  pyrites,  glance,  and  blende ;  3.  with  arsenic, 
as  arsenical  metals ;  4.  with  oxygen,  as  oxides  ;  5.  with 
oxygen  united  with  acids,  as  salts. 

Of  the  best  known  metals,  the  following  occur  the 
most  frequently  a-. — 

1.  Pure.       2.  As  Sulphurets.    3.  As  Arsenical  Metals, 
Gold,  Lead,  Cobalt, 

Platinum,  Antimony,  Nickel, 

Silver,  Copper,  Silver, 

Bismuth,  Silver,  Iron. 

Mercury,  Mercury, 

Arsenic.  Arsenic, 

Iron, 

Zinc. 

4.  As  Oxides.  5.  As  Salts. 

Manganese,  Potassium  and  Sodium, 

Tin,  Barium  and  Strontium, 

Iron,  Calcium  and  Magnesium, 

Chromium,  Aluminium, 

Zinc,  Zinc  and  Iron, 

Uranium,  Lead  and  Copper. 
Copper. 

Classification  of  the  more  common  CJiemical  Elements. 

It  is  very  difficult  so  to  classify  the  chemical  ele- 
ments,—so  to  bring  them,  as  it  were,  into  rank  and 
file,  —  as  to  present  at  the  same  time  a  correct  idea  of 
their  external  and  internal  properties,  and  of  their  affin- 
ities for  each  other.  In  the  following  scheme,  the  two 
elements  which  are  the  most  dissimilar,  the  most  op 
posed,  —  namely,  the  most  electro-negative  (most  acid) 


430 


HEAVY     METALS. 


oxygen,  and  the  most  electro-positive  (most  basic),  potas* 
sium,  —  form  the  two  final  members  of  the  series ;  then 
the  former  is  succeeded  by  those  bodies  which  comport 
themselves  like  oxygen  in  their  properties  and  combina- 
tions, while  potassium  is  followed  by  those  similar  to 
itself.  At  the  junction  of  the  two  series,  the  undecided 
elements  are  found,  —  those  comporting  themselves 
sometimes  negatively  and  sometimes  positively.  If 
it  is  a  law  in  chemistry,  that  bodies  combine  together  so 
*mvch  the  more  eagerly  the  more  dissimilar  they  are  to 
each  other,  while  bodies  similar  in  their  properties  show 
at  most  only  a  very  slight  inclination  to  combine,  then 
this  scheme  may  present  to  us  at  the  same  time  a  prob- 
able idea  of  the  affinities  of  the  elements  for  each  other. 
Those  bodies  most  remote  from  each  other  in  the  series 
have  a  great  desire  to  combine,  while  those  the  nearest  to 
each  other  have  but  little  or  no  desire  to  'unite.  Thus, 
oxygen  most  readily  desires  to  unite  with  the  potas- 
sium, next  with  the  sodium,  next  with  the  calcium, 
barium,  and  so  on ;  it  comports  itself  most  indifferently 
towards  fluorine.  Potassium,  on  the  other  hand,  shows 
the  greatest  affinity  for  oxygen,  then  for  the  salt-form- 
ers, sulphur,  &c. ;  but  the  least  affinity  for  its  neigh- 
bours and  kindred,  sodium,  barium,  &c.  Let  it  be  dis- 
tinctly understood,  however,  that  this  scale  of  affinity  is 
a  very  fluctuating  one,  and  is  subject  in  many  cases  to 
essential  modifications. 


.  RETROSPECT. 


431 


% 

! 

| 

3' 


Oxygen 

» 

Fluorine 
Chlorine 
Bromine 
Iodine 
Sulphur 
Selenium      ^ 
Phosphorus    | 

Nitrogen        s 

1 
Carbon 

Boron 
Silicon 
Arsenic 
Antimony 
Tin 


\ 


Potassium 
£  Sodium 

6 

£  Barium  and  Strontium 


Calcium  and  Magnesium 


|f  Aluminium 

ra 
o5 

§   Chromium 
B* 
^    Manganese 

O 


^    Nickel  and  Cobalt 

*§ 

§    Lead  and  Bismuth 

8 

|    Copper 

i 

|    Mercury 

I" 

^:    Silver 

? 

Platinum  and  Gold 


Hydrogen. 
=b 


PART    SECOND. 

ORGANIC   CHEMISTRY. 

(VEGETABLE  AND  ANIMAL  CHEMISTRY.) 


ORGANIC   CHEMISTRY. 


VEGETABLE    MATTER. 

419.  AN  inscrutable  wisdom  has  given  to  the  seed 
the  po\ver  of  germinating  in  the  moist  air,  and  of 
growing  up  into  a  plant,  which  puts  forth  leaves,  flow- 
ers, and  fruit,  and  then  perishes  and  disappears.  Ger- 
mination, growth,  flowering,  seed-bearing,  and  decay 
are  the  principal  stages  of  existence  through  which  the 
plants  have  to  pass.  When  they  have  produced  seeds, 
that  is,  new  bodies  capable  of  life,  they  have  fulfilled 
their  destiny,  and  their  course  then  tends  downwards 
to  decay.  Whether  they  live  only  one  short  sum- 
mer, or  survive  hundreds  of  years,  the  general  principle 
remains  essentially  the  same. 

The  Divine  agency  which  effects  these  changes,  and 
calls  forth  the  phenomena  of  life  in  the  vegetable  world, 
is,  in  its  essence^  \vholly  unknown  to  us.  A  particular 
name,  vital  power,  has  indeed  been  given  to  it,  but  from 
this  we  derive  no  clearer  conception  or  understanding  of 
it.  Its  operations  are  conducted  in  such  a  mysterious 
manner,  that  it  is  not  probable  that  the  vague  specula- 


4')6  VEGETABLE    MATTER. 

tions  of  the  inquiring  mind  on  this  point  will  ever  lead  to 
bright  or  clear  ideas  here  below.  We  feel,  indeed,  the 
rushing  of  the  vital  current  in  the  joy  which  penetrates 
us  when  in  the  spring  this  force  causes  the  buds  to  ex- 
pand, and  covers  the  earth  with  showers  of  blossoms,  as 
well  as  in  the  melancholy  which  seizes  upon  us  when 
in  the  autumn  the  withering  of  the  leaves  announces  to 
us  its  departure ;  but  whence  this  force  conies,  and 
whither  it  goes,  and  how  it  calls  forth,  as  it  were  by 
magic,  the  wonders  of  the  vegetable  world,  we  are  in- 
deed absolutely  ignorant.  That  only  which  it  produces, 
and  from  which  it  was  produced,  are  comprehensible  to 
our  senses. 

420.  There  are  two  ways  open  to  the  inquirer,  by 
which  he  may  gain  a  partial  insight  into  the  mysterious 
workshop  of  vegetable  life  :  —  1st,  that  of  observation, 
which,  by  the  aid  of  the  microscope  especially,  has  led 
to  a  very  accurate  knowledge  of  the  structure  of  plants, 
and  of  the  changes  which  their  separate  parts  (organs) 
undergo  during  their  growth  ;  2d,  that  of  chemical  ex* 
periment,  by  which  the  constituents  of  plants,  their  food, 
and  some  of  the   transformations   of  matter  occurring 
during  the  growth  of  the  vegetables,  have  been  discov- 
ered.    The  knowledge  acquired  in  these  two  ways  of 
the  inward  and  outward  changes  which  plants  undergo 
during  their  existence,  is  called  vegetable  physiology. 

421.  There   are   generated    in    plants   during   their 
growth  many  substances  having  a  perfect  individuality 
of  their  own>  which  in  many  cases  we  can  distinguish 
from  each  otner  by  their  taste.     Grapes,  carrots,  ar,d 
many  other  fruits  and  roots,  have  a  sweet  taste ;  t'-,ey 
contain  sugar.     The  branches  and  leaves  of  the  g» ape- 
vine  have  a  sour  taste;  they  contain  an  acid  salt.    Those 
of  the  wormwood  have  a  bitter  taste  ;  they  contain  a  pe« 


VEGETABLE    MATTER.  437 

culiar  bitter  principle.  The  latter  emit  also  a  strong  odor, 
which  proceeds  from  a  volatile  oil.  In  the  seeds  of  the 
different  species  of  grain,  and  in  the  tubers  of  the  potato, 
we  find  a  mealy  substance,  starch ;  in  the  seeds  of  the 
rape  and  of  the  flax-plant  a  viscous  juice,  fat  oil.  From 
the  cherry  and  plum  trees  exudes  a  mucilaginous  sub- 
stance, which  *is  soluble  in  water ;  from  the  firs  and 
pines  a  similar  substance,  but  which  is  insoluble  in 
water ;  the  former  we  call  gum,  the  latter  pitch.  The 
magnificent  colors  of  flowers  proceed  from  a  coloring 
matter;  the  noxious  effects  of  poisonous  plants  from 
vegetable  bases,  &c.  These  substances  are  called  by  the 
general  name  of  proximate  constituents  of  plants.  Many 
of  them  are  to  be  found  in  almost  evert/  plant,  while 
others  occur  only  in  particular  species  of  plants. 

We  cannot  imitate  by  art  the  workings  of  nature  in 
living  plants,  as  we  were  able  to  do  most  perfectly  in 
inorganic  chemistry.  The  chemist,  by  chemical  anal- 
ysis, has,  indeed,  determined  with  the  utmost  accu- 
racy of  what  elements  the  proximate  constituents  of 
plants  are  composed,  and  in  what  proportions  by 
weight ;  but  he  has  never  yet  succeeded  in  reconstruct- 
ing these  constituents  from  their  elements. 

422.  Unripe  grapes  taste  sour,  ripe  ones  sweet; 
therefore  we  conclude  that  during  the  ripening  the  acid 
of  the  grapes  has  been  converted  into  sugar.  Common 
barley  tastes  mealy ;  if  suffered  to  germinate  it  ac- 
quires a  sweet  taste,  because  during  germination  a  por- 
tion of  its  starch  is  converted  into  sugar.  Similar 
changes  occur  in  every  living  plant ;  indeed,  they  fre- 
quently take  place  when  the  vital  power  has  become 
extinct  in  the  plant.  Potatoes,  for  instance,  become 
sweet  by  allowing  them  to  freeze ;  all  the  starch  of  the 
germinated  barley  is  converted  into  sugar  by  adding 
37* 


438  VEGETABLE    MATTER. 

water  to  it,  and  letting  it  remain  for  some  hours  in  a 
warm  place.  That  which  is  thus  produced  by  the  vital 
activity  of  the  plants,  or  by  cold  or  heat,  namely,  the 
transformation  of  one  vegetable  substance  into  another 
we  are  also  able  to  effect  by  various  other  means.  Art 
in  this  respect  can  indeed  do  more  than  nature,  since  it 
produces  combinations  —  for  instance,  alcohol,  pyrolig- 
neous  acid,  and  many  other  compounds  —  which  we 
never  find  ready  made  in  the  living  plants.  The  num- 
ber of  these  combinations  may  be  increased  almost  in- 
numerably by  the  aid  of  inorganic  bodies,  such  as  strong 
acids  and  bases,  chlorine,  &c. ;  —  letting  these  operate 
upon  vegetable  substances,  which  are  thereby  changed 
in  an  infinitely  varied  manner,  and  transformed  into 
new  bodies.  Thousands  of  such  new  combinations 
have  been  discovered  within  the  last  twenty  years ;  our 
posterity  will  probably  count  them  by  millions. 

423.  If  you  ask  what  are  the  elements  of  which  the 
proximate   constituents  of  plants   are    composed,   the 
answer  is,  the  four  following  are  the  principal  ones,  — — 
carbon,  hydrogen,  oxygen,   and  nitrogen,  —  which  are 
therefore  called  organogens.      Many  of  the  vegetable 
tissues  contain  all  the  four  elements  (CHON),  and  are 
called  azotized  compounds ;  but  others,  and  by  far  the 
largest   proportion,   contain    only   the    first    three   ele- 
ments (C  H  O),  and  are  called  non-azotized  compounds. 
From  these  few  elements,  with  the  addition  of  small 
quantities  of  sulphur,  phosphorus,  and  some  inorganic 
salts,  the  Creative  Power  is  able  to  produce  the  count- 
less multitude  of  plants  which  cover  the  surface  of  our 
earth. 

424.  If  it  is  obvious,  from  this  simple  constitution, 
that  the  great  variety  of  vegetable  matter  does  not  de- 
pend  up 911  the  number  of  the  constituent  parts,  we 


VEGETABLE    MATTER.  439 

must  presume  that  this  variety  is  owing  to  the  different 
ways  in  which  these  four  elements  are  joined  together 
and  combined  with  each  other.  And  such  is  indeed 
the  fact.  It  has  already  been  mentioned  (§274),  that  in 
the  isomeric  compounds,  that  is,  in  such  as  possess  the 
same  composition,  but  not  the  same  properties,  a  differ- 
ent arrangement  of  the  atoms  is  to  be  supposed;  in 
the  same  manner  as  in  a  chess-board,  where  the  white 


and  black  squares  may  be  grouped  together,  either  2 
and  2,  or  3  and  3,  or  4  and  4,  &c.  This  variety  in 
the  grouping  of  the  atoms,  which  happens  only  as  an 
exception  among  inorganic  substances,  occurs  as  a  gen- 
oral  rule  among  organic  compounds ;  and  it  has  here  so 
much  the  larger  scope,  because  always  three  or  four, 
and  sometimes  even  more  elements,  are  present,  which 
enter  into  combination  with  each  other,  while,  in  the 
department  of  inorganic  chemistry,  commonly  only 
two  elements  unite  with  each  other ;  and  likewise  be- 
cause it  is  a  law  in  organic  chemistry,  that  the  atoms  of 
the  elements  do  not.  unite  singly,  as  with  minerals,  bat 
always  in  groups ;  namely,  2,  3,  4,  6,  8,  10,  or  more  atoms 
of  one  element,  with  any  number  of  atoms  of  the  other 
elements. 

Organic  substances  have,  therefore,  an  incomparably 
more  complicated  constitution  than  the  inorganic  com 
pounds,  as  the  following  examples  show. 

i'Yom  the  well-known  amber,  a  pecu- 
liar acid,  succinic  acid,  is  obtained,  which 
consists  of  four  atoms  of  carbon,  two 
atoms  of  hydrogen,  and  three  atoms  oi 
oxygen,  and  has  accordingly  the  formula 
C4  H.  03  (see  Fig.  165). 


440 


VEGETABLE  MATTER. 


Fi£r.  1(56. 


Fisr.  167. 


If  one  atom  of  oxygen  is  added  to 
this,  we  have  the  constitution  of  malic 
acid  -=  C4  H,O4  (see  Fig  166). 

If  one  more  atom  of  oxygen  is 
added,  that  of  tartaric  acid  =  C4  H, 
O5  (see  Fig.  167). 

And  by  adding  yet  another  atom 
of  oxygen,  that  of  formic  acid=. 
C4  H.  O6  (see  Fig.  168). 

But,  on  the  other  hand,  if  one   atom 
of  hydrogen  is  added  to  the  succinic  acid, 
which  was  the  starting-point,  the  consti- 
tution of  acetic  acid  is  obtained  =  C4  Ha 
O3,  &c.  (see  Fig.  169). 
If  we  are  not  yet  able  to  produce  all  the  transforma- 
tions as  they  are  here  given,  yet  the  possibility  of  suc- 
ceeding at  some  future  time  cannot  be  doubted. 

Sugar,  starch,  and  wood  have  precisely  the  same 
constitution,  namely,  C6  H5  O5 ;  they  are  isomeric.  If 
we  imagine  these  three  elements  grouped  together  in 
different  ways,  as,  for  instance, 

in  starch :  in  wood : 


in  sugar: 

Fig    170. 


Fi?.  171. 


VEGETABLE    MATTER.  441 

then  we  can  form  an  idea  how  one  and  the  same  quan- 
tify of  the  same  elements  may  combine,  forming  such 
very  different  bodies;  and  it  would  not  now  excite  any 
great  astonishment,  if,  on  further  investigation,  hun- 
dreds of  different  substances  of  the  same  constitution 
should  be  discovered,  since,  by  mere  transposition  of 
the  above  sixteen  atoms,  more  than  a  hundred  different 
arrangements  or  groupings  may  be  produced. 

425.  The  instability  of  organized  substances,  which 
has  already  been  referred  to,  is  now  simply  explained 
by  these  complex  proportions  of  the  atoms.  They  are 
like  complicated  machinery.  In  the  spinning-wheel  we 
have  one  wheel,  one  spindle,  and  one  band ;  but  in  a 
spinning-machine,  hundreds  of  wheels,  spindles,  and 
bands,  all  connected  together  into  one  whole.  Now,  as 
in  complicated  machinery  a  wheel  is  more  likely  to 
come  off,  a  spindle  to  bend,  a  wire  to  break,  thereby 
causing  a  greater  disturbance  throughout  the  whole  of 
the  machine  than  can  possibly  happen  in  the  simple 
spinning-wheel,  so  also  complex  organic  bodies  are 
much  more  liable  to  disorganizations  and  changes  than 
the  more  simple  inorganic  bodies.  For  if  in  the  former 
only  one  of  the  many  atoms  leaves,  or  even  changes,  its 
place,  or  if  another  atom,  whether  of  the  same  or  of  a 
different  element,  is  added  to  it,  the  body  at  once  ceases 
to  be  that  which  it  was,  and  becomes  a  new  peculiar 
compound.  The  familiar  terms  combustion,  ignition, 
singeing,  charring,  rotting,  decaying,  fermenting,  curd- 
ling, growing  musty  and  sour,  bleaching,  fading,  &c., 
are  all  chemical  metamorphoses  of  the  kind  referred  to, 
and  it  is  well  known  that  these  metamorphoses  are 
peculiar  to  animal  and  vegetable  substances. 

The  sources  from  which  the  vegetable  world  derives 
its  four  fundamental  substances  (carbon,  hydrogen. 


44*2  VEGETABLE    MATTER. 

oxygen  and  nitrogen),  and  the  form  in  which  it  re- 
ceives them,  will  be  treated  of  more  fully  at  the  close 
of  this  part. 


I.   VEGETABLE   TISSUE. 

426.  Germination  of  the  Seeds.  —  The  vital  force 
slumbers  in  the  seed ;  it  is  called  into  activity  by  moist- 
ure and  heat. 

Experiment.  —  Pour  water  over  some  beans,  and  let 
them  remain  in  a  moderately 
warm  place,  till  the  embryos 
burst  forth,  and  the  swollen  seeds 
divide  into  two  parts.  If  we 
now  examine  them  closely,  we 
shall  perceive  at  the  extremity  of 
each  seed,  where  the  germ  appears,  two  delicate  white 
leaflets ;  from  these,  as  the  plant  continues  to  grow, 
the  stem  and  leaves  are  developed,  while  the  other  ex- 
tremity of  the  germ  forms  into  a  root.  The  solid  mass 
of  which  these  young  organs  consist  is  called  vegetable 
tissue;  it  consists  of  variously-formed  cavities,  which 
sire  filled  with  a  colorless  liquid,  the  sap.  If  the  bean- 
plant  is  exposed  to  the  action  of  light,  a  green  coloring 
matter  (chlorophyll)  is  produced  in  the  sap;  but  this 
substance  is  not  formed  in  the  roots,  since  they  are 
screened  from  the  light  by  the  surface  of  the  earth. 
The  two  lobes  of  the  bean  (cotyledons)  gradually  dis- 
appear as  the  development  of  the  plant  advances; 
they  serve  as  its  first  nourishment.  The  embryo  oi 
most  plants  is  furnished  with  a  pair  of  cotyledons  (dir 
cotyledonous). 


VEGETABLE    TISSUE.  443 

Experiment.  —  Barley,  when  caused  to  germinate  in 
the   same  manner,   puts   forth   only   a    single   embryo, 
Fig.  174.  from  which  first  the  leaves  and  then  the 

stalk  are  developed.  All  our  grasses 
and  bulbous  plants  germinate  in  this 
^manner  (monocotyledonous).  Tf  you 
pour  off  the  water  from  the  barley  when 
the  seeds  are  swelled  and  thoroughly 
steeped,  and  then  put  it  in  a  cool  place, 
piled  up  in  heaps,  you  can,  by  occasion- 
ally turning  it,  so  retard  and  regulate  the  growth 
that  the  radicles  only  will  sprout  forth.  If  you  now 
arrest  further  vegetation  by  quickly  drying  the  grain  in 
a  warm  oven,  the  brewers'  malt  is  obtained.  The  root- 
lets may  be  easily  rubbed  off  after  drying;  they  yield 
an  excellent  manure,  and  consist  principally  of  vege- 
table tissue  rich  in  potassa  and  other  salts,  which  salts, 
during  the  process  of  germination,  have  passed  from 
the  grain  into  the  radicle. 

427.  Vegetable  Tissue.  —  All  the  cells  and  vessels  of 
plants  are  composed  of  vegetable  tissue.  This  sub- 
stance is  to  plants  what  bones,  flesh,  and  skin  are  to 
the  animal  body ;  it  forms  the  solid  mass  of  all  vege- 
table organs,  and  consequently  imparts  to  plants  their 
shape  and  firmness ;  it  forms  the  ducts  or  veins  of  the 
plants,  through  which  the  sap  circulates.  We  find  it 
very  finely  ramified,  tender,  soft,  and  easily  digestible 
in  the  young  leaves,  flowers,  and  stems,  and  in  the  so- 
called  pulp  of  fruit  and  roots,  as  apples,  plums,  carrots, 
&«. ;  hard  and  indigestible  in  straw,  wood  (woody 
tissue),  and  in  the  husks  of  grain  (bran) ;  hardened  like 
stone  in  the  stones  of  plumbs,  cherries,  and  peaches, 
and  in  the  shells  of  nuts;  light,  porous,  and  elastic  in 
the  pith  of  the  elder,  and  in  cork  ;  lengthened  and  pliant 
in  hemp,  flax,  and  cotton. 


444 


VEGETABLE    MATTER. 


428.  The  transverse  section  of  the  stem  of  a  tree 
illustrates  the  influence  which 
age  exerts  upon  the  vegetable 
tissue,  and  how  this  tissue  va- 
ries in  one  and  the  same  tree. 
Inside  the  bark  (a)  lies  the 
inner  fibrous  bark  (b),  which 
consists  of  lengthened  tubes, 
and  is  peculiarly  adapted  to 
supply  the  place  of  veins  in 

the  tree.  Here  the  sap  principally  circulates,  and 
therefore  a  tree  will  die  when  the  inner  bark  is  girdled, 
whilst  (as  seen  in  many  hollow  trees)  the  tree  will  live 
on  if  only  the  inner  and  outer  bark  remain,  though  the 
wood  itself  is  entirely  rotten  and  gone.  From  the 
inner  bark  towards  the  exterior  is  deposited  every 
year  a  new  layer  of  bark,  and  towards  the  centre  a 
new  layer  of  wood  (annual  circles).  The  light  and 
whiter  wood,  lying  next  the  inner  bark,  is  called  the 
sap-wood  (c)  ;  but  this,  by  the  annually  increasing 
compressure,  becomes  denser  and  more  solid,  and  then 
it  is  called  heart-wood  (d).  The  latter  is  usually 
darker,  and  is  frequently  impregnated  with  coloring 
matter  (red-wood).  The  an- 
nexed figure  will  give  an  idea  of 
the  artistical  internal  structure, 
which  is  manifest  even  in  appar- 
ently simple  dense  wood,  as 
viewed  under  a  strong  magni- 
fying-glass.  It  represents  the 
transverse  section  of  a  pine 
bough,  the  portion  marked  a  rep- 
resenting young  ligneous  cells, 
those  marked  b  the  matured 
cells. 


Fig.  176. 


VEGETABLE    TISSUE.  445 

Most  plants  contain  in  the  inner  and  outer  bark  a 
styptic-tasting  substance,  soluble  in  water,  and  which 
is  known  by  the  name  of  tannin,  or  tannic  acid. 

429.  Linen  is  the  inner  bark  of  the  flax-plant.  Dur- 
ing the  process  of  retting-,  the  outer  bark,  by  the  long- 
continued  influence  of  moisture  and  air,  passes  over 
into  decay,  and  then,  after  rapid  drying,  may  be  rubbed 
oil  by  bending  it  backwards  and  forwards  (breaking] ; 
but  the  filaments  of  the  inner  bark,  which  do  not  so 
readily  decay,  remain  behind,  and  after  being  parted 
into  their  finest  fibrils,  and  arranged  parallel  by  the  so- 
called  heckling,  form  the  well-known  flax.  The  tow. 
which  falls  off  during  this  process,  consists  of  tangled 
fibres  of  the  inner  bark. 

Flax  has  a  gray  color,  because  it  contains  a  gray 
coloring  matter,  which  is  not  soluble  in  water  and  lye, 
though  it  becomes  soluble  in  lye  by  exposing  the  flax, 
the  thread  spun,  or  the  linen  woven  from  it,  during  a 
long  time,  to  the  action  of  light,  water,  and  air.  This  is 
done  in  the  bleaching-yard  by  spreading  it  on  the  grass 
(grass  bleaching').  The  coloring  matter,  hereby  altered 
and  rendered  soluble,  is  removed  from  time  to  time  by 
boiling  with  lye.  Bleaching  may  be  accomplished 
more  rapidly  by  the  application  of  chlorine,  which,  on 
account  of  its  very  strong  affinity  for  hydrogen,  attracts 
hydrogen  from  all  organic  substances,  whereby  they  be- 
come colorless  and  soluble  (chlorine  bleaching-).  The 
question  here  occurs,  Why  is  it  that  in  these  two  bleach- 
ing processes  the  coloring  matter  alone,  and  not  the 
vegetable  tissue  at  the  same  time,  is  decomposed  ? 
The  reason  is,  because  the  coloring  matter  consists  of 
four  elements  (CHON),  but  the  vegetable  tissue  of 
only  three  elements  ( C  H  O) ;  according  to  §  425,  the 
more  complicated  substance,  consisting  of  four  ele- 
38 


44£  VEGETABI,E    MATTER. 

ments,  is  more  readily  and  rapidly  decomposed  than 
the  less  complicated  substance,  consisting  of  three  el- 
ements. If,  when  the  linen  has  become  white,  the 
bleaching  were  still  continued  by  either  of  these  meth- 
ods, the  vegetable  tissue  would  then  be  decomposed 
and  become  rotten  ;  a  case  which  often  occurs  when 
linen,  cotton,  or  paper  is  treated  too  lo:ig,  or  with  tco 
strong  a  solution  of  chlorine. 

430.  Bast.  —  Soak   the   bark   of  the  linden-tree  in 
water  till  the  outer  bark  is  decomposed,  and  has  be- 
come brittle ;  when  it  is  dry  the  inner  fibrous  part  of 
the  bark  can  be  peeled  from  it,  and  it  then  forms  the 
linden  bast,  used  for  tying  up  plants.     The  outer  cover- 
ing of  the  trees,  which  is  commonly,  but  erroneously, 
called  bark,  consists  by  no  means  of  the  proper  bark 
alone,  but  of  two  essentially  different  parts,  which  have 
grown  very  closely  together ;  the  external  layer  is  the 
proper  bark  (epidermis),  the  inner  is  the  bast  (liber). 

431.  Cotton  consists  of  delicate  hollow  hairs,  which 
form    in    the    cotton-plant   in    considerable    quantities 
around  the  seeds.     As  it  exists  in  nature  it  is  beauti- 
fully white    (except  the  Nankin  cotton,  which  is  yel- 
low), and  consequently  requires  no  bleaching.     When, 

owever,  cotton  thread  or  cotton  fabrics  are  bleached, 
it  is  merely  in  order  to  remove  the  oily,  sweaty,  and 
mealy  substances  (weaver's  glue,  &c.)  which  have  be- 
come attached  to  them  during  spinning  and  weaving. 
This  is  now  usually  effected  by  boiling  with  soda-lye 
or  milk  of  lime,  or  immersing  them  in  a  weak  solution 
of  chloride  of  lime.  The  lime  which  remain's  adhering 
is  then  removed  by  exceedingly  diluted  acids  (acid 
bath),  and  the  acid,  in  its  turn,  by  rinsing  in  water. 

It  is  well  known  how  important  the  above-mentioned 
sorts  of  pliant  vegetable  tissue  are,  on  account  of  theb 


VEGETABLE    TISSUE.  447 

application  for  making  thread,  twine,  and  fabrics  of 
every  variety ;  we,  clothe  ourselves  in  woody  fibre,  we 
write  and  print  upon  it,  we  build  our  houses  of  it,  &c. 

432.  Vegetable   Tissue  and    Water.  —  Experiment.  — 
Pour  some  lukewarm  water  over  sawdust,  and  let  it 
stand  for  a  day  ;  then  squeeze  out  the  liquid  through  a 
cloth  and  boil  it ;  a  slight  turbidness  will  appear,  and 
on  longer  standing  a  loose  sediment  will  be  deposited. 
Water  does  not  dissolve  the  woody  fibre,  though  it  does 
the  sap  contained  in  it ;  in  this  sap,  as  in  that  of  all 
other  plants,  there  is  always  found  a  substance  in  solu- 
tion, which  is  very  analogous  to  the  white  of  eggs,  and 
which,  like  it,  coagulates  in  boiling ;  it  is  called  vege- 
table albumen.     There  are  also  contained  in  the  liquid, 
separated  from  the  albumen,  various  other  substances 
in  solution  (mucus,  gum,  tannin,  &c.),  which  are  not 
precipitated  by  boiling.      If  the   sawdust,  after  it  has 
been  dried,  is  treated  with  alcohol,  this  will  also  dis- 
solve some  substances    (pitch,  &c.) ;  and  so  also   will 
ether,  lye,  and  other  liquids.     Therefore,  in  the  prepa- 
ration of  perfectly  pure  woody  tissue,  it  must  be  treated 
with  various  solvents  in  order  to  remove  all  the  constit- 
uents of  the  sap. 

CHANGES  OF  VEGETABLE  TISSUE. 

a.}  Changes  of  Vegetable  Tissue  by  Acids. 

433.  Wood,  when  dipped  in  sulphuric  acid,  is  charred ; 
when  in  nitric  acid,  it  is  dyed  yellow,  and  by  longer  im- 
mersion it  is  entirely  decomposed,  as  has  already  been 
observed  (§§  160,  173).      Sulphuric  acid  attracts  from 
lie  woody  fibre  hydrogen  and  oxygen,  which  combine 
to  form  water,  and  then  unite  with  the  sulphuric  acid ; 
nitric  acid  yields  oxygen  to  it,  and  consequently  oxidizes 


448  VEGETABLE    MATTER. 

it.  By  very  long  continued  treatment,  all  the  carbon  of 
the  wood  may  finally  be  oxidized  into  carbonic  acid, 
and  all  the  hydrogen  into  water.  Chlorine  decomposes 
the  vegetable  tissue  by  abstracting  hydrogen  (§429). 
Diluted  sulphuric  acid  operates  very  differently  from 
the  concentrated  acid;  if  paper,  linen,  &c.,  are  boiled 
for  several  hours  with  the  former,  the  vegetable  tissue  is 
converted,  first  into  gum,  and  finally  into  sugar. 

Explosive  Vegetable  Tissue^  or  Gun- Cotton  (Pyroxy- 
lin).—  By  exposing  vegetable  tissue  (cotton,  hemp, 
linen,  sawdust,  &c.)  for  a  short  time  to  the  action  of 
highly  concentrated  nitric  acid,  it  acquires  the  re- 
markable property,  like  that  of  gunpowder,  of  igniting 
and  exploding  with  great  violence  when  touched  by  a 
lighted  match. 

Experiment.  —  Mix  half  an  ounce  of  the  strongest 
nitric  acid  (sp.  gr.  =  1.5)  with  one  ounce  of  strong 
sulphuric  acid ;  pour  the  mixture  into  a  porcelain  mor- 
tar, or  a  cup,  and  press  into  it  with  the  pestle  as  much 
cotton  (wick-yarn,  cotton-cloth,  printing-paper,  &c.)  as 
can  be  moistened  by  the  acid.  When  the  cotton  has 
soaked  for  five  minutes,  it  is  to  be  taken  out  with  a 
glass  rod,  put  into  a  vessel  containing  water,  and 
washed  repeatedly  with  fresh  quantities  of  water,  un- 
til it  no  longer  reddens  blue  test-paper.  The  cotton 
is  then  squeezed  out  with  the  hand,  spread  upon  a 
sheet  of  paper,  and  dried  in  an  airy  place.  It  is  dan- 
gerous to  dry  it  upon  a  stove,  as  it  easily  takes  fire. 

If  the  gun-cotton  thus  prepared  is  struck  smartly  with 
a  hammer  upon  an  iron  anvil,  it  detonates  violently ; 
when  touched  with  a  hot  wire  or  a  lighted  match,  it 
burns  instantaneously,  without  leaving  any  residue ; 
when  fire-arms  are  loaded  with  it,  it  acts  like  gun- 
powder, but  its  explosive  power  is  four  or  five  times? 


VEGETABLE    TISSUE.  449 

greater  than  that  of  the  latter.  Gun-cotton  being,  there- 
fore, an  exceedingly  dangerous  substance,  the  great- 
est caution  is  indispensable  in  conducting  experiments 
with  it,  and  only  very  small  quantities  should  be  used 
at  once.  Gun-cotton  dissolves  in  ether  into  a  sirupy 
liquid,  which  on  spontaneous  evaporation  leaves  the 
cotton  behind  in  the  form  of  a  transparent  film.  This 
solution  is  called  collodium.  It  is  used  instead  of  court- 
plaster,  and  for  making  small  air-balloons,  &c. 

The  chemical  changes  which  cotton  undergoes  by 
immersing  it  in  the  above  acid  mixture  consist  chiefly 
in  this,  that  it  gives  up  a  portion  of  its  hydrogen  and 
oxygen  (as  water),  and  receives  instead  nitric  acid 
(consequently,  nitrogen  with  much  oxygen).  Gun- 
cotton  contains,  therefore,  much  more  oxygen  than  the 
common  cotton,  and  likewise  nitrogen,  in  chemical 
combination  ;  the  former  causes  the  rapid  combustion, 
while  the  latter,  together  with  the  gases  formed  by  the 
combustion,  causes  the  rapid  explosion.  The  sulphuric 
acid  cooperates  only  indirectly,  by  attracting  and  retain- 
ing the  water  contained  in  the  nitric  acid,  and  that 
which  separates  from  the  cotton. 

b.)    Changes  of  the  Vegetable  Tissue  by  Alkalies. 

434.  The  effect  of  alkalies  on  vegetable  tissues  may 
readily  be  seen  by  wrapping  a  piece  of  quicklime  in 
oaper,  and  letting  it  remain  there  for  some  weeks,  when 
the  paper  will  become  quite  rotten.    The  farmer  and  the 
gardener,  being  well  acquainted  with  this  action,  are  ac- 
customed to  mix  in  lime  or  ashes  with  couch-grass  and 
other  weeds,  to  accelerate  the  rotting  and  decay. 

c.)    Changes  of  the  Vegetable  Tissue  by  Heat^  with  free 
Access  of  Air. 

435.  That  wood,  &c.,  when  heated  with  access  oi 

38* 


450  VEGETABLE    MATTER. 

air,  is  consumed,  that  is,  is  decomposed  into  carbon  and 
water,  has  already  been  fully  treated  of  in  the  former 
part  of  this  work.  All  vegetable  substances  are  con- 
sumed in  the  same  way,  by  means  of  the  oxygen  of  the 
air.  If  inorganic  substances  (salts  and  earths)  are 
present,  they,  since  they  are  not  volatile,  remain  be- 
hind as  ashes. 

Vegetable,  and  likewise  animal  substances,  can  be 
consumed,  not  only  by  the  oxygen  of  the  air,  but  also 
by  the  oxygen  of  other  bodies  ;  as,  for  example,  by  that 
of  oxide  of  copper,  of  chromate  and  chlorate  of  potassa, 
or  directly  by  pure  oxygen  Itself.  If  the  water  formed 
during  the  combustion  is  absorbed  by  chloride  of  cal- 
cium, and  the  carbonic  acid  by  a  solution  of  potassa, 
then,  by  the  increased  weight  of  the  chloride  of  calcium 
and  the  potassa,  the  quantity  of  the  water  and  of  the 
carbonic  acid  may  be  ascertained,  and  from  these  the 
weight  of  the  hydrogen  and  carbon  which  the  con- 
sumed body  contained  may  be  calculated.  That  which 
is  wanting  in  the  weight  of  the  original  body  under 
examination  is  the  amount  of  oxygen  which  it  con- 
tained. In  this  manner  the  three  elements  comprised 
in  an  organic  body,  carbon,  hydrogen,  and  oxygen, 
may  be  very  accurately  determined  ;  such  an  exami- 
nation is  therefore  called  an  elementary  analysis.  If,  in 
addition  to  the  three  above-named  elements,  an  organic 
body  contains  nitrogen  also,  it  escapes  uncombined 
during  the  combustion  in  the  form  of  gas,  and  can  be 
collected  and  estimated  by  a  special  method  of  analysis. 
But  on  heating  such  bodies  with  bases  having  a  strong 
affinity  for  water,  —  for  instance,  with  hydrate  of  po- 
tassa or  soda  and  lime,  —  then  (with  but  few  excep- 
tions) the  nitrogen  contained  in  them  escapes  in  com- 
bination with  hydrogen,  as  ammonia,  from  which  the 
contents  of  nitrogen  can  be  accurately  calculated. 


VEGETABLE    TISSUE. 


451 


d.)  Oiang-es  of  the  Vegetable  Tissue  by  Heat,  the  Access 
of  Air  being  prevented. 

436.  Imperfect  Combustion  of  Wood.  —  When  wood 
is  heated  with  insufficient  access  of  air,  as  is  the  case, 
for  instance,  in  most  of  our  stoves,  a  portion  of  the  car- 
bon remains  un burnt,  and  is  deposited  as  soot  from  the 
gases  which  form  the  flame.  Moreover,  during  the  pro- 
cess, a  portion  of  the  burning  carbon  takes  up  only 
half  as  much  oxygen  as  when  there  is  an  abundant 
supply  of  air,  and  there  is  formed,  not  only  carbonic 
acid,  but  also  carbonic  oxide  gas  (fumes  of  charcoal). 
But,  besides  these  compounds,  other  singular  sub- 
stances are  formed,  as  is  indicated  by  the  peculiar  smell 
of  the  smoke,  and  by  the  lustrous  acid  and  resinous 
soot  deposited  upon  the  lower  parts  of  chimneys. 
The  products  of  the  decomposition  of  vegetable  tissue 
may  be  more  clearly  recognized  if  you  heat  the  wood 
with  entire  exclusion  of  air. 

Experiment. —  Subject  wood,  as   was   described  in 

Pig.  177. 


§  119,  to  dry  distillation;  you  obtain  a  great  variety  of 
products  easily  to  be    distinguished  by  characteristic 


452  VEGETABLE    MATTER. 

properties  ;  —  1.  charcoal,  which,  since  it  is  not  volatile, 
remains  behind ;  2.  illuminating  gas,  a  mixture  of  car- 
buretted  hydrogen,  carbonic  acid,  and  carbonic  oxide 
gases ;  3.  wood-vinegar,  a  watery  acid  liquid ;  4.  wood- 
tar,  a  thick,  brown,  resinous  liquid.  The  two  former 
substances  have  been  already  described,  so  that  only 
the  two  latter  remain  to  be  more  fully  considered. 

437.  Pyroligneous  Acid,    or   Wood-  Vinegar.  —  One 
pound  of  dry  beech-wood  yields  nearly  half  a  pound  of 
pyroligneous  acid.     In  its  crude  state  it  has  a  brownish- 
black  color,  owing  to  the  tar  which  it  contains  in  solu- 
tion, and  a  smoky  odor,  together  with  a  very  acid,  dis- 
agreeable, smoky  flavor.     On  account  of  its  containing 
acetic  acid,  and  its  cheapness,  it  is  now  much  used  in 
the  preparation  of  acetates,  particularly  such  as  are  em 
ployed   in    calico-printing   and    dyeing  ;    for   instance, 
acetate  of  iron,  of  lead,  of  soda,  &c. 

Experiment.  —  Pour  some  wood- vinegar  upon  a  piece 
of  lean  meat,  and  let  it  soak  for  a  few  hours ;  it  can 
then  be  dried  and  packed  without  passing  into  putre- 
faction, as  in  a  few  hours  it  has  experienced  the  same 
change,  and  acquires  the  same  degree  of  firmness, 
usually  produced  by  being  suspended  for  months  in  the 
smoke  (rapid  smoking"). 

438.  Wood-vinegar  owes  its  antiseptic  properties  to 
a  peculiar  substance,  which  has  received  the  name  of 
creosote  (flesh-preservative) ;  one  pound  of  pyroligneous 
acid  contains  about  a  quarter  of  an  ounce  of  it  in  solu- 
tion.    Pure  creosote  is  a  colorless  liquid,  gradually  be- 
coming brown  by  age,  and  of  an  oily  consistency ;  it 
has  a  strong  smell  of  smoke,  a  very  burning  taste,  and 
disorganizes  the  tender  skin  of  the  tongue  or  the  mouth, 
and,  taken  internally,  is  a  powerful  poison.     Creosote  is 
now  frequently  applied  as  a  remedy  for  the  toothache, 


VEGETABLE    TISSUE.  453 

when  it  is  usually  mixed  with  oil  of  cloves  ;  but  it  must 
also  be  diluted  with  alcohol,  in  which  it  readily  dis- 
solves, as  its  action  would  otherwise  be  too  corrosive. 
One  dram  of  water  will  dissolve  one  drop  of  creosote; 
this  solution  (creosote-water,' 01  aqua  Binelli),  which 
acts  upon  flesh  in  the  same  manner  as  the  pyroligneous 
acid,  is  employed  as  a  sedative.  The  smoke  which  is 
formed  in  our  stoves  by  the  incomplete  combustion  of 
wood,  or  of  pit-coal,  always  contains  fumes  of  creosote, 
to  which  is  owing  its  peculiar  smell,  and  its  property  of 
causing  lachrymation.  Every  thing  which  prevents 
complete  combustion,  such  as  a  deficient  draught  oi 
air,  or  moist  fuel,  must,  accordingly,  favor  the  forma- 
tion of  creosote,  and  render  the  smoke  more  irritating. 
Flesh  is  most  effectually  cured  by  this  smoke,  which  is 
expressly  generated  for  this  purpose  by  burning  green 
fagots,  or  obstructing  the  draught  of  air. 

439.  When  pyroligneous  acid  is  very  slowly  distilled, 
a  spirituous,  volatile  liquid,  very  similar  to  brandy,  first 
passes  over,  which  is  called  crude  pyroxilic  spirit.     The 
chief  component  of  this  fluid  is  a  substance  which,  in 
its  properties  and  changes,  has  great  similarity  to  alco- 
hol, or  spirits  of  wine,  though  its  constitution  is  differ- 
ent.    On  account  of  this  similarity,   it  is  called   py- 
roxilic spirit  (hydrated  oxide  ofmethyle). 

440.  Wood-tar  is  of  a  resinous  nature,  that  is,  in- 
soluble in  water,  though  soluble  in  alcohol;  it  is  more- 
over very  rich  in  carbon,  as  is  in  some  degree  indicated 
by  its  black  color.     On  distillation,  it  separates  into  a 
volatile  oil   (oil  of  tar),  and  into   a  non-volatile  black 
pitch   (§  576).     This   separation  takes  place,   also,  but 
more   slowly,  when  wood    is  smeared    with    tar;    the 
pitch,   hardening  in  the  pores  of  the  wood,  then  pre- 
vents the  penetration  of  the  water,  and  hereby,  as  by 


454  VEGETABLE    MATTER. 

the  creosote  also  contained  in  the  tar,  the  decompose 
tion  of  the  wood  by  putrefaction  is  arrested  (tarring 
and  calking  of  ships,  &c.). 

The  dry  distillation  of  wood  shows  in  a  very  strik- 
ing manner  with  what  extraordinary  readiness  organic 
substances  may  be  decomposed  and  transformed  into 
very  remarkable  new  bodies.  The  wood  has  only  to 
be  heated  in  order  to  be  resolved  into  an  acid  and  a 
spirituous  body,  —  into  oily  and  resinous  substances, — 
into  illuminating  gas  and  carbon.  And  these  are  not 
all  the  products  of  the  decomposition  of  wood.  Be- 
sides the  substances  here  mentioned,  a  dozen  others,  at 
least,  have  been  discovered,  which  are  generated  simul- 
taneously with  them,  and  each  of  which  may  be  con- 
verted by  heating,  by  treating  with  acids,  bases,  chlo- 
rine, &c.,  into  numerous  other  bodies.  Here  a  great 
field  opens  for  chemical  investigation,  a  field  which  has 
indeed  no  bounds,  and  which  must  be  so  much  the 
more  extended,  since  all  vegetable  matter,  heated  with 
exclusion  of  air,  becomes  charred  and  decomposed  into 
products  of  combustion,  but  which  are  different  in  different 
bodies,  as  is  obvious  in  the  dry  distillation  of  tobacco 
in  tobacco-pipes,  of  pit-coal,  brown  coal,  &c. 

441.  Imperfect  Combustion  of  Pit-  Coal  —  Pit-coal  and 
brown  coal  are  formed  from  the  vegetables  of  a  for- 
mer era,  which  were  washed  together  in  heaps  during 
some  revolution  of  the  earth,  and  deeply  buried  be- 
neath mud  and  soil.  When  pit-coal  is  heated  with  ex- 
clusion of  air,  we  obtain,  in  the  same  manner  as  from 
wood,  —  1.  carbon  (coke);  2.  a  combustible  gas  (illu- 
minating gas)  ;  3.  an  aqueous,  empyreumatic  liquid 
(tar-water) ;  and  4.  a  resinous,  black,  viscid  liquid  (pit 
coal  tar). 

The  aqueous  empyreumatic  liquid  obtained  from  pit- 


VEGETABLE     TISSUE.  455 

coal  contains  only  a  trace  of  vinegar,  but  in  large! 
quantities  a  basic  body,  ammonia,  combined  with  car- 
bonic acid ;  it  may  therefore  be  employed  as  a  manure, 
or  for  the  preparation  of  sal  ammoniac. 

The  pit-coal  tar,  which  is  now  very  generally  em- 
ployed for  smearing  over  wood,  iron,  and  the  roofs  of 
buildings,  to  protect  them  from  moisture,  may  aho, 
like  wood-tar,  be  separated  by  distillation  into  a  vol- 
atile substance  (oil  of  coal-tar),  and  into  a  pitchy,  non- 
volatile substance  (artificial  asphaltum) ;  but  the  pe- 
culiar substances  (kyanole,  pyrrol,  leucol,  carbolic  acid, 
rosolic  acid,  brunolic  acid,  naphtaline,  &c.)  contained 
in  the  latter  are  quite  different  from  those  of  the  former. 
Of  these  substances,  naphtaline^  a  white,  camphor-like 
body,  has  been  examined  most  closely ;  but  the  names 
only  of  some  of  the  new  combinations  resulting  from 
these  researches  will  here  be  mentioned,  to  show,  alas ! 
with  what  a  flood  of  new  and  strange  names  this  sin- 
gle substance  has  inundated  chemistry.  The  follow- 
ing compounds  are  formed  by  the  action  of  nitric  acid 
upon  naphtaline:  nitronapht-alase,  -aleise,  -alise,  -ale, 
-esic  acid,  -isic  acid,  phtalic  acid,  phtalamide,  &c. ;  by 
treating  with  chlorine:  chloronaphta-lase,  -lese,  -lise, 
-lose,  &c. 

442.  A  decomposition  similar  to  that  which  pit-coal 
undergoes  during  dry  distillation  must  also  be  pro- 
duced, perhaps,  in  many  places  in  the  interior  of  the 
earth,  by  volcanic  heat,  for  we  know  that  in  many 
countries  substances  either  issue  from  the  earth,  or  are 
imbedded  in  it,  which  have  a  very  great  similarity  to 
the  products  of  the  distillation  of  pit-coal,  as  is  shown 
in  the  following  arrangement. 


456 


VEGETABLE  MATTER. 


Artificially  produced 
from  Pit-Coal.  Occurring  Native  in  the  Earth. 

a.)  Illuminating  gas.  a.)  Inflammable  gases  (sacred  fire  of  the  Bra- 

mins),  issuing  here  and  there  from  the 

crevices  of  rocks. 

6.)   Oil  of  coal-tar.  6.)  Naphtha,  oozing  out  of  the  earth  in  Persia. 

«.)   Oil  of  coal-tar.  c.)   Mineral  tar,  found  in  many  places  in  Persia 

and  France. 

el.)  Artificial  asphaltum      d.)  Natural  aspltaltum   (pitch  of  Judea),  found 

(pitch  of  pit-coal).  in  the  Dead  Sea,  and  other  Asiatic  seas. 

e.)  Ammomacal  empyreu-      e.)  Ammonia,  issuing  in  a  watery  vapor,  associ- 

matic  liquid.  atcd  with   boracic  acid,  from  the  earth 

near  Tuscany. 
f.)    Coke  (C).  /.)   Anthracite   (C),  like  pit-coal,  occurring  in 

immense  beds  in  the  earth. 

e.)    Changes  of  the  Vegetable  Tissue  by  Air  and   Watei . 
(Decay  and  Putrefaction.) 

443.  Decay.  —  When  vegetable  tissue  — for  instance, 
wood,  leaves,  straw,  &c. — is  exposed  to  the  influence 
of  the  air,  it  imbibes  moisture,  and  becomes  gradually 
brown  and  rotten,  —  it  passes  into  decay.  The  chem- 
ical process  which  thus  takes  place  very  much  resem- 
bles those  changes  which  wood  undergoes  in  combus- 
tion, except  that  it  takes  place  far  more  slowly ;  what  is 
effected  by  combustion  in  minutes  is  effected  by  decay 
only  in  the  course  of  years.  By  combustion,  the  con- 
stituents of  the  wood  and  the  oxygen  of  the  air  are 
converted  into  carbonic  acid  and  water ;  the  same  prod- 
ucts are  also  formed  on  the  decay  of  wood.  In  com- 
bustion, the  hydrogen  is  oxidized  more  rapidly  than 
the  carbon ;  the  same  happens  also  in  decay.  This  ex- 
plains why  wood,  on  combustion,  as  well  as  on  decay, 
assumes  a^darker — first  a  brown,  and  then  a  black- 
color.  When  proportionably  more  hydrogen  passes 
off  than  carbon,  the  residue  must  necessarily,  as  the 
decomposition  continually  progresses,  be  richer  in  car- 


VEGETABLE    TISSUE.  457 

bon,  and  consequently,  as  a  general  rule,  also  of  a  dark- 
er color. 

444.  Humus.  —  The  brown  or  black  substance  into 
which  vegetable  matter  is  converted  by  decay  has  re- 
ceived the  name  humus.  As  wood,  which  is  only  par- 
tially consumed,  can  be  consumed  still  further,  so  also 
humus  is  gradually  further  decomposed,  and  in  most 
cases,  after  complete  combustion  or  decay,  there  is  final- 
ly left  only  a  small  quantity  of  non-volatile  salts  and 
earths,  —  the  ashes,  —  which  the  wood  has  absorbed  from 
the  earth  during  its  growth.  If  these  two  processes  of 
decay  are  supposed  to  be  going  on  in  two  distinct  peri- 
ods, then  there  are  formed,  — 


.    (  water   (much).  (  water  (much), 

from  the  wood  in  J  ^^          '        from  the  wood  in  )  carbonic  ^ 

the  1st  period,     (  half-burnt  wood;     the  1st  period,      (  humus  . 

tort  Jort  in  thl  (  Water  (Httle)'         from  the  huraus  J  water  <little)> 
2d  period  (  carbonic , acid ;         in  the  2d  period,  (  carbonic  acid ; 

there  remain,        ashes.  there  remain,          ashes. 

Humus  is  identical  with  decaying  Organic  Matter. — 
In  this  acceptation  it  has  for  many  years  been  known 
and  valued  in  agriculture.  Vegetable  mould  (humus) 
is  the  term  applied  to  the  upper  blaclPor  brown  layer  of 
earth,  which  has  been  formed  in  forests  by  the  decay  of 
the  leaves  which  fall  off;  the  dark,  fat,  arable  soil,  con- 
taining much  partially  decomposed  organic  master,  is 
said  to  be  rich  in  humus,  while  the  dry,  light  soil,  in 
which  it  is  wanting,  is  said  to  be  poor  in  humus.  The 
farmer  knows  that,  contrary  to  what  happens  in  his 
woodlands,  the  humus  diminishes  in  his  fields,  and  so 
much  the  more  rapidly  as  the  crops  are  more  abundant ; 
he  knows  that  fields  rich  in  humus  are,  as  a  general 
39 


458  VEGETABLE     MATTER. 

rule,  more  fertile  than  those  which  are  poor  in  humus. 
Therefore  he  seeks  to  restore  to  his  land  the  humus 
consumed  in  vegetation  by  ploughing  in  straw  and 
animal  excrements  (manuring),  or  fresh  plants  (green 
manuring),  or  by  the  alternation  of  plants  which  leave 
behind  many  roots  in  the  soil  (fallow  plants)  with 
such  as  are  only  feebly  rooted  (grain).  On  an  acre 
of  land  which  was  cultivated  with  clover,  several  thou- 
sand pounds  of  roots  remained  behind  in  the  soil; 
upon  one  cultivated  with  wheat  or  grain,  only  from 
one  fifth  to  one  sixth  as  much ;  it  is  therefore  appar- 
ent, that  in  the  former  case  from  five  to  six  times  more 
humus  must  be  generated  by  the  decay  of  the  roots 
than  in  the  latter.  The  increase  of  fertility  which  the 
farmer  thus  aims  at  is,  however,  by  no  means  to  be  as- 
cribed to  the  humus  alone,  since  the  inorganic  constit- 
uents (salts  and  earths)  which  are  present  in  manure 
and  in  the  soil  have  a  principal  share  in  it  (§  611). 

If  we  consider  the  formation  of  humus,  we  shall  at 
once  perceive  that  various  substances  are  included  un- 
der this  term ;  for  its  constitution  alters  every  day,  since 
a  little  of  its  carbon  and  hydrogen  is  every  day  oxid- 
ized and  separated.  We  may  easily  conceive,  that  very 
old  humus  may^contain  as  much  again  carbon  as  that 
which  is  recent,  or  even  more.  The  ideas  concerning 
humus  became  still  more  vague  when  chemists  first 
thought  of  designating  by  this  name  other  brown  and 
black  colored  substances,  the  products  of  the  evapora- 
tion of  vegetable  juices  or  decoctions,  or  which  were 
formed  from  wood,  starch,  sugar,  &c.,  by  boiling  the 
latter  with  acids  or  alkalies.  The  term  humus  thus  be- 
came, as  it  were,  a  foundling-hospital,  into  which  were 
bi  ought  all  the  substances  formed  from  vegetable  or  an- 
in,  il  matter,  provided  they  were  black  or  brown,  and 


VEGETABLE    TISSUE.  459 

were  insoluble,  or  nearly  insoluble,  in  water.  The 
humus  generated  by  decay,  as  we  find  it  in  ara- 
ble soil,  is  now  thought  to  be  a  mixture  of  several 
distinct  brown  substances,  namely,  of  ulmine,  hu- 
mine,  ulmic  acid,  humic  acid,  geic  acid,  crenic  and 
apocrenic  acids,  which  are  produced  consecutively, 
according  to  the  above  series,  from  vegetable  mat- 
ter. The  two  latter  acids  are  soluble  in  water,  and 
are  partly  the  cause  of  the  yellow  or  brownish  color 
which  we  perceive  in  the  water  of  marshes  or  bogs ; 
the  other  three  acids  are  only  soluble  in  water  when 
alkalies  are  added ;  finally,  the  first  two  substances,  ul- 
mine and  humine,  can  neither  be  made  soluble  by  wa- 
ter nor  by  alkalies.  Accordingly,  by  the  general  term 
humus  we  must  understand  a  mass  of  brown  decaying 
matter,  partly  soluble,  partly  insoluble,  partly  acid, 
partly  neutral,  which,  with  the  uninterrupted  presence 
of  air,  water,  and  heat,  maybe  still  further  decomposed, 
and  thereby  carbonic  acid  and  water  evolved.  Car- 
bonic acid  and  water  are  indispensable  to  the  nour- 
ishment of  plants;  hence,  in  a  soil  rich  in  humus, 
the  plants  will  grow  more  vigorously,  because  they 
find  there,  and  can  absorb  by  their  rootlets,  more  of 
these  two  nutritive  substances  than  they  could  in  a 
soil  poor  in  humus.  Humus  exerts,  moreover,  a  bene- 
ficial influence  upon  vegetation,  because  it  loosens  the 
soil  by  the  development  of  carbonic  acid,  because  it 
possesses  the  power  of  attracting  water  from  the  air,  and 
of  retaining  it  for  a  long  time,  and  because,  by  means 
of  the  acids  contained  in  it,  it  is  able  to  abstract  from 
the  air,  and  also  from  manure,  the  third  means  of  nutri- 
ment for  plants,  ammonia. 

445.  Putrefaction.  —  The  decomposition  of  vegetable 
tissue  takes  place    in    a   somewhat    different  manner 


460 


VEGETABLE     MATTER. 


Fig.  178. 


when  the   air  is  entirely  or  partially   excluded, — for 
instance,  when   the  decomposition  takes   place  under 
water,  as  we  observe  in  ponds,  marshes,  and  rivers. 
Experiment. — Thrust  a  pole  into  the  mud  of  a  pond, 

and  catch  the  bubbles 
which  rise,  in  a  bottle 
filled  with  water,  and 
held  inverted  over 
them;  when  all  the 
water  is  displaced  from 
the  bottle,  close  it  up 
while  under  the  water. 
Introduce  a  little  wa- 
ter into  the  bottle,  and 
afterwards  a  small 

piece  of  caustic  potassa  or  quicklime,  close  it  immedi- 
ately, shake  it  a  few  minutes,  and  then  remove  the  stop- 
per under  the  water ;  a  part  of  the  water  will  press  into 
the  bottle,  because  the  bases  have  absorbed  a  portion  of 
the  gas.  The  gas  absorbed  was  carbonic 
acid.  If  you  now  apply  a  burning  match 
to  the  mouth  of  the  bottle,  and  expel  the 
remainder  of  the  gas  by  pouring  in  wa- 
ter, it  will  ignite  and  burn  with  a  blue 
flame.  This  is  called  marsh  gas  (light 
carburetted  hydrogen  gas) ;  it  consists  of 
carbon  and  hydrogen,  like  the  common 
illuminating  gas,  but  it  contains,  com- 
pared with  this,  a  smaller  quantity  of  carbon,  and  there- 
fore burns  without  giving  a  bright  light.  These  two 
gases,  carbonic  acid  and  marsh  gas,  originated  in  the 
wood,  leaves,  branches,  roots,  &c.,  of  the  vegetables 
which  sunk  to  the  bottom  of  the  water,  and  were  there 
decomposed. 


Fig.  179. 


VEGETABLE    TISSUE. 


461 


When  oxygen  is  wanting,  the  hydrogen  of  the  vege- 
table tissue  combines  with  a  portion  of  the  carbon, 
while,  if  there  is  an  abundant  supply  of  oxygen,  the 
hydrogen  unites  with  the  latter.  Here,  too,  a  substance 
similar  to  humus,  and  richer  in  carbon,  remains  behind; 
in  ponds,  as  a4  black  mud,  in  marshes,  as  peat.  This 
kind  of  decomposition  is  called  putrefaction;  it  is  some- 
what analogous  to  the  change  which  wood  undergoes 
on  incomplete  combustion  (charring,  dry  distillation)^  as 
is  shown  by  the  following  arrangement :  — 


In  charring, 


In  putrefaction, 


Mie  vegetable  tis- 
sue is  convert-  < 
ed  into 

a.)  illuminating 
gas, 
6.)  carbonic  acid, 
c.)  partially  con- 
Isumed    sub- 
stances (tar, 
coke,  &c.). 

the  vegetable  tis- 
sue is  convert- 
ed into 


a.)  marsh  gas, 
b.)  carbonic  acid, 
c.)  partially  rot 
ted  substan 
ces      (mud, 
peat). 


446.  Peat  is  formed  from  marsh  plants,  which  slowly 
rot  under  water;  every  year  a  new  vegetation  arises, 
which,  on  perishing,  sinks  to  the  bottom,  and  tnus,  in 
the  course  of  time,  a  morass  is  formed.     The  young 
peat  consists  of  a  brown,  fibrous  network,  in  wnich  the 
separate    parts    of   the    plant   may    be    clearly    distin- 
guished ;  but  after  a  time  it  decomposes  into  a  black, 
3lirny  mass,  which  may  be  cut  into  pieces  of  the  shape 
oforieks.     The  old,  black  turf  only  smoulders  away  on 
burning,  a  proof  that  the  hydrogen  of  the  plants  from 
which  it  was  formed  has  mostly   disappeared  daring 
putrefaction. 

447.  As  above  stated,  carbonic  acid  was  continually 
generated  in  the  formation  of  peat;  a  portion  of  this 
carbonic  acid  remains  in  solution  in  the  water,  and 
this  explains  why  the  water  which  percolates  through 

39* 


462  VEGETABLE    MATTER. 

beds  of  peat  into  the  earth,  and  reappears  as  springs 
in  deeper  places,  often  contains  so  much  carbonic 
acid  that  it  can  be  used  as  mineral  water  (acidulous 
springs).  If  the  water  during  its  course  meets  with 
rocks  containing  protoxide  of  iron,  lime,  magnesia, 
&c.,  it  may,  by  means  of  its  carbonic  acid,  dissolve 
small  quantities  of  them  (§§  237,  276).  In  this  man- 
ner many  of  the  mineral  waters  occurring  in  nature 
originate,  as,  for  instance,  the  celebrated  Marienbader 
springs,  &c. 

448.  Besides  peat,  we  find  two  other  vegetable  sub- 
stances in  the  earth,  which  are  likewise  used  as  fuel,  on 
account  of  their  richness  in  carbon,  —  brown  coal  and 
pit-coal.  Both  are  the  remains  of  a  vegetation  which 
covered  the  earth  before  it  was  inhabited  by  man.  It  is 
highly  probable  that  they  were  formed  from  the  vege- 
tables and  trees  of  a  primeval  age,  when,  by  inundation, 
or  some  other  violent  revolution  which  the  crust  of  the 
earth  underwent,  they  were  buried  under  immense  beds 
of  sand  and  clay,  and  were  there  decomposed  by  a  pro- 
cess similar  to  that  of  putrefaction,  while  the  sand 
hardened  into  sandstone,  and  the  clay  into  slaty  clay 
or  shale.  In  those  places  where  the  layers  of  earth 
were  not  sufficiently  strong  to  prevent  the  escape  of  the 
carbonic  acid  and  of  the  marsh  gas,  we  often  find,  as, 
for  instance,  in  many  species  of  brown  coal,  the  form 
of  the  wood  so  well  preserved,  that  the  annual  ri^gs 
may  be  distinguished  in  it  (bituminous  wood) ;  but  in 
other  places  the  wood  is  transformed  into  a  brown 
mass,  which  has  a  strong  resemblance  to  humus,  or 
peat  (brown  coal).  But  if  the  pressure  of  the  superin- 
cumbent mass  of  earth  was  so  strong  as  to  prevent  the 
escape  of  the  gases  formed  during  the  decomposition 
of  the  imprisoned  plants,  they  must  necessarily  have  re* 


VEGETABLE    TISSUE.  463 

mained  behind  with  the  coal.  This,  together  with  the 
compressure  of  the  weight  of  a  layer  of  earth  or  stone 
a  thousand,  perhaps  several  thousand,  feet  thick,  ac- 
counts for  the  dense,  compact,  stone-like  nature  of 
many  kinds  of  coal,  especially  of  pit-coal,  and  also  for 
their  property  $f  burning  with  a  flame.  Those  gases 
which  were  condensed  in  the  coal  we  obtain  again,  as 
illuminating  gas  and  carbonic  acid,  when  we  heat  the 
coal  in  a  retort. 

It  is  generally  known  that  moist  vegetable  matter,  as 
grass,  hay,  manure,  &c.,  becomes  hot,  and  is  converted 
into  a  black,  carbonaceous  rich  mass,  when  piled  to- 
gether in  compact  heaps.  This  smouldering  sort  of 
carbonization,  taking  place  here  on  a  small  scale,  mu&t 
occur  also  on  a  large  scale,  when,  by  some  revolution  of 
the  earth,  masses  of  plants  are  washed  together  in 
heaps,  and  covered  over  with  mud ;  and  this  smoulder- 
ing must  be  so  much  the  more  complete  the  greater 
is  the  pressure  under  which  the  decomposition  takes 
place,  and  the  longer  the  time  occupied  in  effecting 
it.  Pit-coal  is  usually  found  at  greater  depths  in  the 
earth,  and  between  older  layers  of  rocks  (in  the  tran- 
sition rocks),  than  the  brown  coal,  which  mostly  oc- 
curs nearer  the  surface  of  the  earth,  between  more 
recent  layers  of  rocks  (in  the  tertiary  rocks)  ;  we 
therefore  conclude  that  the  formation  of  pit-coal  com- 
menced at  an  earlier  period,  and  that  of  brown  coal 
not  till  a  later  period.  The  extraordinary  differences 
occurring  in  this  process  of  decomposition,  according 
to  the  variety  of  plants,  and  the  cooperation  of  more 
or  less  water,  heat,  air,  pressure,  &c.,  are  very  evident 
in  the  extraordinary  variety  of  the  products  formed. 
Many  of  the  pit  and  brown  coals  burn  with  a  vivid 
flame,  others  with  a  feeble  one,  and  some  without 


464  VEGETABLE    MATTER. 

any  ;  many  melt  in  the  heat,  others  crumble  to  a  sandy 
powder ;  many  yield  but  one  per  cent,  of  ashes,  while 
others  yield  from  25  to  30  per  cent.,  &c. 

449.  White  Rotten  Wood.  —  Experiment.  —  Put,  dur- 
ing the  summer,  some  sawdust,  moistened  with  water, 
in  a  closed  vessel,  and  let  it  stand  for  some  months  ; 
the  wood  will  gradually  lose  its  firmness,  and  be  con- 
verted into  -a  white.)  friable  substance.  A  splinter  of 
wood  will  not  continue  to  burn  in  the  air  of  the  vessel, 
since  the  air  no  longer  contains  free  oxygen,  but  car- 
bonic acid.  The  water,  too,  has  disappeared :  it  has 
chemically  combined  with  the  woody  tissue.  A  similar 
transformation  frequently  occurs  in  the  interior  of  the 
trunks  of  trees,  where  the  air  cannot  have  free  access ; 
the  well-known  white  rotten  wood  is  formed  in  this 
way.  When  the  air  has  free  access,  a  brown  substance 
(humus,  ulmine)  is  produced,  such  as  occurs  in  hollow 
elms,  willows,  lindens,  and  other  trees. 

The  decomposition  to  which  wood  is  exposed  by  de- 
cay and  putrefaction  may  be  retarded  and  checked^  — 

1.  By  rapid  drying,  whereby  the  water  of  the  sap  is 
removed. 

2.  By  steeping  in  water  or  steam,  by  which  process 
the  sap  is  dissolved  and  removed. 

3.  By  smearing  with  bodies  which  prevent  the  pene- 
tration of  the  water ;  for  instance,  with   varnish,  tar, 
pitch,  &c. 

4.  By  impregnating  with  saline  solutions,  which  act 
antiseptically*;   for   instance,   with  corrosive  sublimate 
(kyanizing),  salts  of  lime,  iron,  &c. 


STARCH.  465 


II.   STARCH,   OR  FECULA. 

450.  A  MEALY  substance,  which  is  known  under  the 
name  of  starch,  or  fecula,  is  deposited  in  most  vege- 
tables, particularly  at  the  period  of  ripening,  from  the 

juices    with   which    the   cells    of    the 
Fig.  iso.  piants  are  fiUed> 

It  appears  to  the  naked  eye  like 
particles  of  meal,  but  under  a  power- 
ful microscope  it  is  found  to  consist  of 
small,  generally  regular  grains  or  glob- 
ules. Their  position  in  the  plant  is 
shown  in  the  annexed  figure,  which 
represents  a  section  of  some  of  the 
cells  of  a  potato. 

If  a  fresh  plant  is  bruised  and  macerated  in  water, 
and  the  liquid  then  squeezed  out,  a  large  portion  of  the 
starch  will  pass  with  the  juice  from  the  vegetable  tissue, 
and  will  settle,  after  standing  quietly  awhile,  as  a  mealy 
mass.  Potatoes,  grain,  and  leguminous  plants  are  very 
rich  in  starch. 

451.  Potatoes.  —  Experiment.  —  Rasp  some  potatoes 
on  a  grater,  knead  the  pulp  thus  obtained  with  water, 
and  squeeze  it  in  a  linen  cloth  ;  the  fibrous  particles  of 
the  cells  remain  behind,  but  the  juice,  together  with  a 
large  portion  of  the  starch,  runs  through.     If  you  let  the 
turbid  liquid  remain  quiet  for  some  hours,  it  becomes 
clear,  because  the  heavier  starch  settles  at  the  bottom. 
Now  decant  the  liquid,  wash  the  starch  several  times 
with  fresh  water,  allowing  it  to  settle  each  time,  and 
then  dry  it  in  a  moderately  warm  place. 

Experiment.  —  Heat  in  a  flask  the  clear  liquid  de 
canted  from  the  starch ;  it  becomes  turbid  when  tha 


466  VEGETABLE    MATTER. 

neat  approaches  the  boiling  point,  and,  after  boiling 
for  a  few  moments,  deposits  a  flaky,  grayish-white  sub- 
stance, which  is  to  be  collected  on  a  filter.  It  is  the 
same  substance  already  referred  to  (§  432),  vegetable  al- 
bumen, characterized  by  its  property  of  dissolving  in 
cold  and  warm  water,  but  of  coagulating  in  boiling 
water.  It  contains  nitrogen,  which  the  starch  does  not. 

Experiment.  —  Put  some  of  the  coagulated  albumen 
upon  a  piece  of  platinum  foil,  and  heat  it  over  a  lamp ; 
it  will  burn  and  emit  a  very  disagreeable  empyreumatic 
odor.  When  starch  is  treated  in  the  same  manner,  it 
also  gives  off  an  empyreumatic,  but  far  less  unpleasant 
smell.  All  azotized  substances  comport  themselves  in 
this  respect  like  albumen ;  all  non-azotized  substances, 
like  starch ;  therefore,  when  a  piece  of  woollen  cloth  is 
singed,  it  diffuses  a  far  more  disagreeable  odor  than 
a  piece  of  cotton  or  linen,  because  nitrogen  is  contained 
in  the  wool,  but  not  in  the  cotton  or  linen. 

A  freshly-cut  potato  has  a  white  color,  which,  how- 
ever, on  longer  exposure  to  the  air,  passes  over  to 
brown;  a  similar  change  takes  place  in  the  liquid 
pressed  out  from  the  grated  potatoes ;  at  first  it  is  color- 
Jess,  but  gradually  becomes  darker.  The  substance, 
not  yet  accurately  studied,  which  effects  this  change  of 
color,  is  designated  by  the  general  term  coloring  matter; 
it  is  soluble  in  water,  as  is  evident  from  the  last-men- 
tioned property. 

Experiment.  —  Mix  twenty  drops  of  sulphuric  acid 
with  three  ounces  of  water,  and  pour  this  acid  water 
upon  a  potato  cut  in  thin  slices  ;  after  standing  twenty- 
four  hours,  the  slices  are  to  be  taken  out,  and  washed 
with  water  till  they  have  no  longer  an  acid  taste,  and 
then  dried.  During  this  process  the  potatoes  lose  theii 
juices,  and  also  their  albumen  and  coloring  matter,  and 


STARCH,  467 

after  drying  form  a  solid,  mealy,  white,  and  tasteless 
substance,  which  swells  up  and  becomes  soft  when  boil- 
ing water  is  poured  upon  it.  Potatoes  dried  without 
this  treatment  become  gray  and  horn-like,  and  acquire 
an  unpleasant  smell. 

452.  Peas.  -$-  Experiment.  —  Pour  a  handful  of  peas 
into  a  capacious  vessel  containing  water,   and  let  it 
stand  for  some  days  in  a  warm  room ;  a  great  part  of 
the  water  is  absorbed  by  the   peas,  causing  them  to 
swell  up,  and  finally  to  become  so  soft  that  they  can 
easily  be  mashed  between  the  fingers.     When  in  this 
state  bruise  them  in  a  mortar,  and  add  sufficient  wa- 
ter to  form  with  them  a  thin   paste,   which   may  be 
squeezed  out  by  means  of  a  linen  cloth.     Here,  also,  we 
obtaint  as  from  potatoes,  —  1.  a  fibrous  substance,  which 
remains  on  the  cloth ;   2.  starch,  which  is  deposited, 
after  standing,  from  the  turbid  liquid  ;  3.  vegetable  albu- 
men,  when  the  decanted  liquid  is  heated  to  boiling. 

Experiment.  —  When  you  have  separated,  by  boiling 
and  filtering,  the  vegetable  albumen  from  the  above- 
mentioned  liquid,  add  to  the  latter  a  few  drops  of  some 
kind  of  acid  ;  a  flaky  white  body  will  once  more  be  de- 
posited ;  this  is  called  vegetable  caseine  (cheesy  matter), 
on  account  of  its  great  similarity  to  the  cheese  con- 
tained in  milk  (animal  caseine)  in  its  constitution  and 
also  in  its  properties.  Vegetable  caseine,  like  vegetable 
albumen,  contains  nitrogen;  but  it  is  distinguished  from 
the  latter  by  this,  namely,  that  it  is  not  coagulated  by 
boiling,  though  it  is  by  acids.  It  occurs  in  the  juice  of 
many  plants,  but  it  is  most  abundant  in  the  seeds  of 
leguminous  plants ;  potatoes,  likewise,  contain  small 
quantities  of  it. 

453.  Wheat  Flour.  —  Experiment.  —  Moisten  a  hand- 
ful of  wheat  flour  with  sufficient  water  to  form  a  stiff 


468  VEGETABLE    MATTER. 

paste  when  triturated  in  a  mortar ;  inclose  it  in  a  piece 
of  thick  linen,  and  knead  it  frequently,  adding  water  as 
long  as  the  liquid  which  runs  through  continues  to  have 
a  milky  appearance.  After  standing  some  time,  a 
white  powder  will  settle  from  the  turbid  water :  this  is 
wheat  starch. 

Starch  is  one  of  the  principal  constituents  of  flour,  as 
indeed  of  all  sorts  of  rrieal ;  the  second  constituent  re- 
mains behind  in  the  cloth,  mixed  with  vegetable  fibre, 
and  is  a  viscous,  tough,  gray  substance,  which  has  re- 
ceived the  name  gluten  (vegetable  fibrine).  The  gluten 
only  swells  up  in  water,  without  being  completely  dis- 
solved ;  in  its  constitution  it  corresponds  exactly  with 
albumen,  and,  like  this,  contains  nitrogen. 

When  the  water  decanted  from  the  starch  is  boiled, 
it  becomes  turbid,  and  when  partially  evaporated  yields 
a  flocculent  precipitate  ;  thus  wheat  meal  contains  also 
some  vegetable  albumen. 

454.  If  the  results  of  these  experiments  are  grouped 
together,  we  shall  find  that  there  are  always  present  in 
potatoes  and  peas,  and  also  in  wheat  flour,  the  two 
non-azotized  substances  vegetable  tissue  and  starch, 
and  also  one  or  several  of  the  azotized  compounds  veg- 
etable albumen,  caseine,  and  gluten. 

Non- Azotized  Substances. 
In  potatoes  :  vegetable  tissue,  starch  ; 
In  peas  :  vegetable  tissue,  starch ; 
In  wheat  :  vegetable  tissue,  starch. 

Azotized  Substances. 

In  potatoes  :  vegetable  albumen,  caseine  (little) ; 
In  peas  :  vegetable  albumen,  caseine  (much)'; 
In  wheat :  vegetable  albumen,  gluten  (much). 

The  three  substances  above  named,  containing  nitro- 


STARCH.  409 

and  sulphur,  have  the  general  name  of  albuminous 
compounds ;  hitherto  they  have  been  called  proteinaceous 
compounds.     Small  quantities  of  one  or  more  of  them 
occur  in  the  sap  of  every  plant. 

455.  Potato  starch  exhibits,  under 
the  microscope,  the  form  of  egg-shaped 
grains,  consisting  of  many  scales  over- 
lapping each  other ;  it  glistens  in  the 
sun,  is  hard  to  the  touch,  and  has  al- 
ways more  of  a  pulverulent  than  of  a 
concrete  character. 

In  the  starch  of  peas  many  of  the 
grains  are  concave  in  the  direction  of 
their  length,  while  others  seem  to  be 
formed  by  the  growing  together  of  sev- 
eral globules. 

Wheat  starch  consists  of  dull,   flat- 
tened,  lenticular   grains,  which,  when 
\   /0  (?Vl      m°ist)  readily  adhere  to  each  other,  on 
which    account    the    wheat    starch   of 
0         commerce  always  comes  in  loose  lumps. 
CJ  (/>  o^  «         When  ground,  it  is  known  under  the 

name  of  hair-powder,  8fC. 

Arrowroot  is  a  starchy  meal  used  in  medicine,  which 
is  prepared  in  the  East  and  West  Indies  from  the  roots 
of  some  marsh  plants. 

456.  Experiment.  —  If  some  starch  is  placed  in  a 
ladle,  and  gently  heated  with  constant  agitation  till 
dried  up,  hard,  horny  granules  are  obtained,  which 
swell  when  boiling  water  is  poured  on  them,  and  be- 
come gelatinous  and  translucent;  these  granules  are 
called  sago.  The  genuine  sago  comes  from  India, 
where  it  is  prepared  from  starch,  which  is  extracted 
from  the  pith  of  many  of  the  palm-trees. 
40 


170  VEGETABLE    MATTER. 

We  find  the  starch  granules  swollen  by  water,  also, 
in  boiled  potatoes.  One  pound  of  crude  potatoes  con- 
tains about  three  quarters  of  a  pound  of  watery  juice, 
and  from  two  ounces  to  two  and  a  half  of  starch ;  at 
the  heat  of  boiling  water  or  steam,  this  juice  is  ab- 
sorbed by  the  starch,  so  that  the  swollen  grains  fill  up 
the  cells,  which  thereby  acquire  a  round  shape.  The 
annexed  figure  represents  the  magnified 
reticulated  cells  caused  by  the  coagulated 
albumen  of  the  juice,  which  fills  up  the 
interstices  between  the  single  granules. 
All  our  baked  food  contains  starch  as  its 
principal  ingredient,  and  owes  to  it  its  friable  and  light 
character. 

457.  Experiment.  —  Heat  in  a  vessel  half  a  dram  of 
starch,  with  an  ounce  or  an  ounce  and  a  half  of  water, 
constantly  stirring  it  till  it  boils ;  the  mixture  first  be- 
comes slimy,  and  finally  as  thick  as  a  jelly.  The  grains 
of  starch  absorb  water,  and  swell  up,  so  that  the  single 
membranes  break  open.  This  swollen  starch  is  well 
known  for  its  adhesive  properties,  and  is  variously  em- 
ployed as  a  means  of  thickening  printing  colors.  When 
linen  and  other  woven  fabrics  are  passed  through  a  thin 
paste  of  starch,  they  acquire,  after  drying,  a  degree  of 
stiffness,  and  by  ironing  or  strong  rubbing  and  press- 
ing a  bright  gloss  (dressing).  The  swelling  of  many 
of  our  most  common  articles  of  food,  such  as  rice, 
groats,  barley,  beans,  peas,  lentils,  &c.,  when  boiled 
with  water,  is  now  readily  explained  by  their  containing 
a  large  quantity  of  starch. 

Experiment.  —  If  you  let  some  starch  paste  remain 
for  a  length  of  time  in  a  warm  place,  it  gradually  be- 
comes thin  and  sour ;  it  thus  passes  into  a  peculiar  acid, 
which  has  received  the  name  of  lactic  acid.  The  same 


STARCH.  47J 

acid  is  produced  when  milk  becomes  sour,  and  it  im« 
parts  to  curdled  milk  and  to  buttermilk  their  well- 
known  sour  taste. 

Experiment.  —  Dilute  some  starch  paste  with  a  large 
proportion  of  water,  and  add  to  it  a  few  drops  of  tinc- 
ture of  iodine  (§  155)  ;  an  intensely  deep  blue  liquid 
(iodide  of  starch)  is  produced.  The  same  color  may 
be  perceived  by  dropping  some  tincture  of  iodine  upon 
meal,  potatoes,  carrots,  &c.  We  have  in  iodine  an  ex- 
tremely delicate  test  for  starch. 

There  is  a  peculiar  species  of  starch  called  muline, 
which  occurs  in  the  roots  of  the  elecampane  and  the 
dandelion,  and  in  the  bulbs  of  the  dahlia  ;  this  is  colored 
yellow  by  the  tincture  of  iodine. 

Another  variety  of  starch,  which  is  colored  brown  by 
the  tincture  of  iodine,  is  found  particularly  in  Iceland 
moss,  and  is  called  lichenine. 

Change  of  Starch  into  Gum  and  Sugar. 

458.  Starch  Gum.  —  Experiment.  —  If  starch  is  heat- 
ed in  a  ladle  over  a  gentle  alcohol  flame,  and  during  the 
heating  (roasting)  is  constantly  stirred  to  prevent  its 
burning  and  baking  on  the  bottom  of  the  ladle,  it  ac- 
quires after  a  while  a  yellow,  and  finally  a  brownish- 
yellow  color,  and  then  possesses  the  new  property  of 
dissolving,  both  in  cold  and  in  hot  water,  into  a  muci- 
laginous liquid.  (Common  starch  is  entirely  insoluble 
in  cold  water,  and  only  swells  up  in  hot  water.)  Starch 
thus  transformed  is  called  roasted  starch,  starch  gum,  or 
le'iocome.  It  is  well  adapted  for  the  thickening  of  colors 
and  mordants  in  calico-printing,  and  therefore  is  now 
often  made  on  an  extensive  scale,  usually  by  roasting 
starch  in  large  coffee-roasters. 

Experiment.  —  Mix  thoroughly,  in  a  smah1  dish,  hal/ 


472  VEGETABLE    MATTER. 

an  ounce  of  starch  with  one  dram  of  water  arid  four 
drops  of  nitric  acid ;  let  the  mixture  dry  in  the  air,  and 
then  place  it  on  the  hearth  of  a  heated  oven,  which  is 
just  hot  enough  to  hiss  feebly  when  touched  with  the 
moistened  finger.  After  some  hours,  all  the  nitric  acid 
will  be  expelled,  and  the  starch  will  dissolve  almost  en- 
tirely in  cold  water,  and  completely  in  hot  water. 
Starch-gum  thus  made  is  white,  or  has  only  a  slight 
yellowish  tinge. 

Experiment.  —  Make  a  paste  of  potato  starch  by 
boiling  starch  with  water,  and,  while  yet  hot,  add  to  it, 
in  a  saucer,  some  drops  of  sulphuric  acid,  with  constant 
stirring.  That  this  acid  effects  a  change  is  evident,  for 
the  viscid  mass  very  soon  becomes  a  thin  liquid.  Now 
place  the  saucer  on  a  jar,  in  which  some 
water  is  simmering  (steam-bath),  and  let  it 
remain  over  the  hot  steam  (the  contents  of 
the  saucer  not  being  heated  quite  to  the 
boiling  point),  until  the  liquid  has  become 
semi-transparent.  When  this  is  the  case, 
add  prepared  chalk  by  small  portions  at  a  time  to  the 
liquid,  until  it  ceases  to  give  an  acid  reaction,  and  after 
having  filtered  it  from  the  gypsum,  leave  it  to  evapo- 
rate in  a  warm  place.  The  dry  residue  has  an  amor- 
phous, vitreous  appearance,  an  insipid  taste,  and  dis- 
solves in  water,  forming  a  transparent  viscid  fluid ;  it 
is  not  soluble  in  alcohol.  Vegetable  substances  with 
such  properties  are  usually  called  gums  ;  the  gum  ob- 
tained from  starch  has  received  the  special  name  of 
dextrine. 

459.  Starch- Sugar. — Experiment.  —  Repeat  the  for- 
mer experiment,  with  the  following  deviation.  Bring 
to  brisk  boiling  two  ounces  and  a  half  of  water,  to 
which  twenty  drops  of  sulphuric  acid  have  been  add- 


STARCH.  473 

ed,  and  then  add  one  ounce  of  starch  mixed  with  a 
little  watery  forming  a  paste,  but  only  in  small  quan- 
tities at  once,  that  the  boiling  may  not  be  interrupted. 
When  all  the  starch  is  stirred  in,  let  the  mixture  boil 
for  some  minutes,  then  neutralize  the  acid  by  chalk, 
and  evaporate  ^the  filtered  liquid  to  the  consistency  of  a 
thick  sirup.  It  possesses  a  very  sweet  taste,  and  con- 
sists of  a  solution  of  sugar  in  water.  The  starch-sirup 
thus  made,  as  well  as  the  white,  solid  starch-sugar, 
easily  prepared  from  it,  are  now  both  articles  of  com- 
merce. 

Starch,  as  shown  by  these  experiments,  is  converted 
by  sulphuric  acid,  on  moderate  heating,  into  gum  ;  on 
stronger  heating,  into  sugar.  In  the  latter  case,  also, 
dextrine  is  first  formed,  but  this  soon  passes  over  into 
sugar.  Accordingly,  sulphuric  acid  exerts  two  different 
actions.  By  the  first  action,  the  starch  becomes  gum 
(dextrine).  By  the  second  action,  the  dextrine  becomes 
sugar. 

It  has  not  yet  been  explained  how  this  effect  is 
produced.  Starch,  starch-gum,  and  starch-sugar  have 
each  the  same  constitution  (isomeric),  so  that  their 
difference  undoubtedly  depends  upon  a  different  ar- 
rangement of  the  atoms  of  carbon,  hydrogen,  and  oxy- 
gen contained  in  them,  and  it  is  undoubtedly  the  sul- 
phuric acid  which  effects  this  change  in  the  position  of 
the  atoms.  No  portion  of  the  sulphuric  acid  has  been 
decomposed,  neither  has  any  of  it  combined  with  the 
organic  substance ;  for  we  find  again,  in  the  gypsum 
formed,  exactly  the  same  quantity  of  sulphuric  acid  thai 
had  been  originally  employed.  Accordingly,  in  this  case 
it  exerts  an  action  quite  different  from  the  usual  action ; 
it  is  an  action  like  that  of  spongy  platinum,  which  can 
excite  a  chemical  activity  in  another  substance,  without 
40* 


474  VEGETABLE    MATTER. 

itself  undergoing  any  change.  This  peculiar  mode  of 
action  of  sulphuric  acid  and  -of  platinum  is  often  desig- 
nated by  the  name  of  "  action  of  presence  "  (contact),  or 
action  by  catalysis  (power  of  conversion). 

460.  Malt  and  Diastase.  —  Experiment.  —  Pour  two 
ounces  of  lukewarm  water  upon  a  quarter  of  an  ounce 
of  coarsely  pulverized  barley-malt ;  let  the  mixture  re- 
main some  hours  near  a  fire  or  stove,  or  in  the  sun, 
and  then  strain  it  through  a  linen  cloth ;  there  is  found 
in  the  filtrate  a  substance  not  yet  well  known,  called 
diastase,  by  means  of  which  the  starch  may  be  con- 
verted into  gum  and  sugar  in  the  same  way  as  by  sul- 
phuric acid. 

Experiment.  —  Rub  a  quarter  part  of  the  diastase 
with  some  hot  starch  paste,  made  of  a  quarter  of  an 
ounce  of  potato  starch  and  two  ounces  of  water ;  heat 
the  mixture  moderately  (but  not  above  65°  C.),  until 
the  paste  is  formed  into  a  thin,  transparent  liquid. 
Now  boil  this  liquid  for  some  time  at  a  stronger  heat, 
strain  through  a  cloth,  and  let  it  evaporate  in  a  warm 
place.  The  mass  remaining  behind  is  like  that  ob- 
tained at  §  458,  and  consists  of  dextrine,  or  starch-gum. 

Experiment.  —  Treat  the  other  three  quarters  of  the 
diastase  in  the  same  way,  but  prolong  the  heating  for 
several  hours,  which  may  be  most  conveniently  done 
on  the  hearth  of  a  stove  or  fireplace,  applying  to  the 
liquid  a  heat  not  above  70°  or  75°  C.  Here  also  dex- 
trine is  the  first  product  formed ;  but  this  is  soon  con- 
verted on  further  boiling  into  starch-sugar,  as  may 
easily  be  perceived  by  its  taste.  By  evaporation,  sirup 
of  starch  is  obtained,  as  in  §  459. 

461.  The  remarkable  change  which  malt  communi- 
cates to  starch  is  to  be  ascribed  to  the  diastase  con- 
fined in  the  malt.     This  substance  obviously  acts  in  a 


STARCH.  475 

very  similar  manner  to  sulphuric  acid,  but  its  mode  of 
action  is  as  yet  likewise  unknown.  At  100°  C.,  conse- 
quently, on  boiling  the  liquid,  the  effect  of  the  malt 
(diastase)  is  destroyed.  The  process  of  forming  sugar 
by  means  of  the  diastase  of  malt  is  of  great  impor* 
tance  to  the  l^rewer  and  brandy-distiller,  as  in  the 
manufacture  of  beer  from  barley  or  wheat,  or  brandy 
from  rye  and  potatoes,  the  starch  of  these  substances 
must  always  be  previously  converted  into  sugar,  before 
fermentation  and  the  consequent  formation  of  alcohol 
can  take  place.  In  both  cases  it  is  the  diastase  of  the 
malt,  indispensable  in  brewing  and  in  the  distillation 
of  brandy,  which  effects  this  change  in  the  so-called 
mashing  process. 

462.  The  taste  of  malt  is  sweet  and  mucilaginous, 
because  the  conversion  of  the  starch  into  dextrine  and 
sugar  commences  during  germination,  the  further  prog- 
ress of  which  is  arrested  in  this  case  by  drying.  If 
the  germinated  barley  is  allowed  to  continue  growing, 
as  it  does  in  the  open  fields,  all  the  starch  gradually 
vanishes  from  the  grain,  and  passes,  in  the  form  of  dex- 
trine and  sugar,  into  the  juice  of  the  young  plant,  as 
is  obvious  from  the  sweet  taste  of  the  latter,  and  from 
its  mucilaginous  feeling  when  rubbed  between  the 
fingers. 

A  similar  metamorphosis  is  also  clearly  to  be  per- 
ceived in  the  potatoes.  The  quantity  of  starch  con- 
tained in  one  hundred  pounds  of  the  same  kind  of  po- 
tatoes has  been  found  to  be,  in  August,  10  pounds  ;  in 
September,  14;  in  October,  15;  in  November,  16;  in 
December,  17;  in  January,  17;  in  February,  16;  in 
March,  15;  in  April,  13;  in  May,  10.  Accordingly 
the  quantity  of  starch  in  potatoes  increases  during  the 
autumn,  remains  stationary  during  the  winter,  and  in 


476  VEGETABLE    MATTER. 

the  spring,  after  the  germinating  principle  is  excited,  it 
diminishes.  It  is  a  well-known  fact,  that  on  germina- 
tion potatoes  become  soft,  mucilaginous,  and  afterwards 
sweet;  the  dextrine  forming  from  the  starch  renders 
them  mucilaginous,  and  the  sugar  forming  from  the 
dextrine  renders  them  sweet.  This  process  of  trans- 
formation advances  still  further  in  the  earth,  the  pota- 
toes becoming  constantly  softer  and  more  watery,  and 
when  the  starch  is  completely  consumed  in  the  growth 
of  the  young  plant,  the  process  of  decay  commences, 
and  its  products,  carbonic  acid,  water,  and  ammo- 
nia, may  be  regarded  as  food  for  the  somewhat  older 
plant. 

463.  Unripe  apples  and  pears  are  colored  blue  by 
tincture  of  iodine;  consequently  they  contain  starch. 
When  completely  ripe,  they  cease  to  give  this  reaction ; 
therefore  starch  has  disappeared  on  ripening,  as  ap- 
pears by  the  taste  of  the  fruits;  they  are  sweet,  and 
we  must  therefore  presume  that  here  also  a  transfor- 
mation of  the  starch  into  dextrine  and  sugar  has  taken 
place.  It  appears,  also,  that  frost  is  capable  of  exert- 
ing a  similar  influence  upon  these  vegetable  substances, 
which  are  rich  in  starch  ;  it  is  well  enough  known,  that 
frozen  potatoes,  apples,  medlars,  &c.  have  a  sweet  taste 
after  being  thawed. 


III.    GUM   AND   VEGETABLE   MUCUS. 

464.  IT  has  already  been  explained,  when  speaking  oi 
dextrine,  what  kind  of  vegetable  matter  is  called  gum, 
and  likewise  that  it  is  an  intermediate  substance  be- 
tween starnh  and  sugar.  Dextrine  is  one  of  the  most 


GUM  AND  VEGETABLE  MUCUS.  477 

widely  diffused  substances  in  the  vegetable  kingdom, 
since  we  find  it  in  greater  or  less  quantities  in  the  juice 
of  every  plant. 

But  there  exist  in  many  plants  certain  sorts  of  gum, 
and  sometimes  in  such  abundance,  that  they  exude 
from  the  bark  a£  a  viscid  liquid,  and  harden  upon  it  in 
transparent  globular  masses,  such  as  we  see  on  our 
peach  and  cherry  trees.  The  name  resin,  by  which 
these  dried  vegetable  juices  are  frequently  designated, 
is  erroneous,  because  by  resins  are  meant  those  vege- 
table juices  which  do  not  dissolve  nor  soften  in  water, 
but  are  soluble  in  alcohol.  The  action  of  gum  is  dif- 
ferent ;  this  is  insoluble  in  alcohol,  but  is  softened  and 
dissolved  by  water. 

465.  Gum  Arabic.  —  The  best  known  of  these  pecu- 
liar sorts  of  gum  is  gum  Arabic,  which  exudes  spon- 
taneously from  several '  species  of  acacia  in  Africa. 
The  finer  sorts  of  it  are  white,  the  more  common  kinds 
have  a  yellow  or  brown  color.  When  well  dried,  it  is 
so  hard  and  brittle  that  it  may  be  reduced  to  a  powder 
by  pounding. 

Experiment.  —  Pour  two  drams  of  cold  water  on  one 
dram  of  gum  Arabic,  and  occasionally  stir  the  mixture  ; 
the  gum  will,  after  a  few  days,  entirely  dissolve  in  the 
water,  forming  a  viscid  transparent  mucilage ,  which 
may  be  diluted  at  pleasure  with  more  water.  This 
mucilage  has  great  adhesiveness,  for  which  reason  it  is 
often  used,  instead  of  paste  or  glue,  for  joining  together 
paper,  &c.,  or  for  converting  a  pulverulent  substance 
into  a  coherent  mass  (crayons,  pastilles,  &c.) ;  it  has, 
moreover,  a  thick  consistency,  and  hence  is  variously 
employed  in  calico-printing  as  a  thickening  material  for 
colors  and  mordants,  and  in  finishing  and  dressing 
operations.  A  variety  of  gum  obtained  from  the  shores 


478  VEGETABLE    MATTER. 

of  the  Senegal,  whence  it  has  been  called  gum  Senegal, 
h  peculiarly  well  adapted  for  the  latter  purpose,  as 
it  yields  a  thicker  mucilage  than  the  common  gum 
Arabic. 

Experiment.  —  Pour  some  drops  of  mucilage  of  gum 
Arabic  into  alcohol ;  they  will  not  mix  with  each  other, 
as  the  gum  is  insoluble  in  alcohol.  If  the  mucilage  is 
previously  mixed  with  water,  forming  a  thin  clear  liquid, 
and  is  then  added  to  the  alcohol,  a  turbidness  ensues, 
and  afterwards  a  flaky  precipitate  will  subside ;  accord- 
ingly, alcohol  may  be  used  for  removing  gum  from 
those  liquids  which  contain  gum. 

In  a  chemical  sense,  only  those  sorts  of  gum  are 
designated  by  the  name  of  gum  which  dissolve  com- 
pletely in  cold  water,  and  thus  form  a  clear,  transparent 
liquid. 

466.  Gum  tragacanth  is  also  a  vegetable  exudation, 
well  known  as  a  stiffening  material,  and  as  forming 
with  water  an  adhesive  paste;  it  exudes  from  the  tra- 
gacantha,  a  shrub  which  grows  in  Greece  and  Turkey, 
and  it  occurs  in  commerce  in  the  form  of  white,  tortuous 
filaments,  or  bands. 

Experiment.  —  Let  a  piece  of  tragacanth  remain  for 
some  days  in  cold  water ;  it  will  soften  and  swell  into 
a  stiff,  viscid  jelly;  a  single  dram  of  it  is  sufficient  to 
convert  one  pound  of  water  into  a  thick  mucilage. 
The  tragacanth  does  not  dissolve,  but,  like  starch, 
only  sivells  up ;  if  the  mucilage  is  boiled,  the  mass  be- 
comes more  uniform,  but  a  complete  solution  is  not 
effected. 

This  kind  of  gum  has  been  called  vegetable  mucus 
(bassorine),  to  distinguish  it  from  the  former;  it  occurs 
also  in  many  other  plants,  as,  for  instance,  in  the  leaves 
of  the  mallows  and  the  coltsfoot,  in  the  roots  of  the 


SUGAR.  479 

althea  and  salep,  in  flax  and  quince  seeds,  and  in  car- 
rageen, &c.  This  mucilage  abounds  in  the  cores  of  the 
quince,  for  it  surrounds  the  seeds  as  a  whitish,  transpar- 
ent substance  ;  it  must  obviously  be  very  plentiful,  since 
one  dram  of  quince-cores  is  sufficient  to  convert  half  a 
pound  of  waterunto  a  thick  mucilage. 

467.  Experiment.  —  If  you  pour  a  large  quantity  of 
water  upon  some  of  the  gum  of  cherry  or  plum  trees, 
part  of  the   gum   will   be   dissolved  after  some  time, 
but  a  part  will  remain  undissolved  as  a  turgid  mass 
(vegetable  mucus,  cerasine).     These  two  vegetable  ex- 
udations must  accordingly  be  regarded  as  mixtures  of 
gum  and  vegetable  mucus. 

468.  Pectine.  —  The  juices  of  many  fruits  and  roots, 
for   instance,   currants,    gooseberries,   cherries,   apples, 
carrots,  &c.,  contain  a  peculiar  kind  of  mucus,  which 
communicates  to  the  juice  the  property,  especially  when 
previously  boiled  with  sugar,  of  hardening  into  a  gelat- 
inous mass  after  cooling.     This  mucus,  to  which  the 
stiffening  of  +he  juice  is  to  be  ascribed,  has  received  the 
special  name  of  pectine  (vegetable  jelly). 


IV.    SUGAR    (SACCHARUM). 

469.  Sugar  of  Starch. —  The  manner  of  converting 
starch  into  sugar  has  already  been  described  under  the 
head  of  Starch.  This  sugar  may  be  prepared  in  two 
ways ;  either  by  boiling  with  diluted  sulphuric  acid 
(sirup  of  starch),  or  by  digesting  the  starch  with  malt  or 
diastase  (malt  sirup).  Both  of  these  sirups  may  be  re- 
garded as  concentrated  solutions  of  sugar  in  water.  li 
a  very  concentrated  sirup  of  starch  is  allowed  to  remain 


480  VEGETABLE    MATTER. 

standing  for  some  time,  a  granular  sediment  separates 
from  it,  while  a  par^  of  the  solution  of  sugar  remains 
fluid  and  ropy.  The  solid  sugar  thus  obtained,  which 
consists  of  fine  granules,  is  called  starch-sugar,  and  the 
liquid  portion,  which,  even  on  being  evaporated  to  dry- 
ness,  always  again  attracts  moisture  and  deliquesces, 
is  called  liquid  sugar. 

Honey  bears  a  strong  resemblance  to  starch-sugar. 
If  it  is  kept  for  some  time  after  being  melted,  the  mass, 
at  first  homogeneous,  likewise  separates  into  two  parts, 
into  a  granular  solid  residue,  and  into  a  sirupy  liquid. 
The  former  consists  of  starch-sugar,  the  latter  of  liquid 
sugar. 

This  species  of  sugar  (starch-sugar)  is  formed  also  in 
many  vegetables,  and  is  especially  abundant  in  fruits ; 
as,  for  example,  in  plums,  cherries,  pears,  figs,  grapes, 
&c.  The  white  coating  of  prunes  and  the  white,  sweet 
grains  in  raisins  consist  of  it.  On  account  of  this  origin, 
sugar  of  starch  is  also  called  grape-sugar. 

If  you  taste  a  dried  granule  of  sugar  from  a  raisin, 
and  then  a  little  common  sugar,  you  will  at  once  per- 
ceive that  the  former  is  much  less  sweet  than  the  latter ; 
one  ounce  of  common  sugar  has  the  same  sweetening 
capacity  as  two  ounces  and  a  half  of  grape-sugar.  The 
solubility  of  these  two  varieties  of  sugar  in  water  is 
likewise  very  different,  grape-sugar  dissolving  in  it 
much  less  readily  and  more  slowly  than  common  sugar. 
While  one  ounce  of  cold  water  can  dissolve  three 
ounces  of  common  sugar,  it  is  able  to  take  up  only 
two  thirds  of  an  ounce  of  grape-sugar ;  the  solution  of 
sugar  (sirup)  prepared  from  the  former  is,  accoidingly, 
of  a  much  stronger  and  more  tenacious  consistency 
than  that  prepared  from  grape-sugar. 

470.   Cane-  Sugar.  —  Our  common  sugar  is  different 


SUGAR.  481 

from  those  kinds  of  sugar  just  described ;  it  is  eithei 
prepared  in  the  tropical  regions,  from  the  juice  of  the 
sugar-cane  (cane-sugar),  or  in  France  and  Germany, 
from  the  juice  of  the  beet  (beet-sugar). 

The  operations  whereby  this  sugar  is  obtained  on  a 
large  scale  are  the  following :  — 

1.  Expressing1  the  juice  from  the  sugar-cane  or  the 
rasped  pulp  of  the  beet,  either  by  strongly  squeezing,  o; 
by  hydrostatic  pressure. 

2.  Boiling  down  the  juice  with  the  addition  of  lime, 
by  which  several  foreign  substances   are  precipitated, 
until  it  acquires  the  consistency  of  a  thick  sirup  ;  on 
cooling,  the  crude  sugar  is  deposited  from  it,  in  brown- 
ish-yellow crystalline  grains  (raw  sugar,  or  Muscovado 
sugar).     The  liquid  sugar  which  does  not  crystallize  is 
allowed  to  drain  off,  and  forms  the  well-known  brown 
sirup  (molasses). 

3.  Refining  the  raw  sugar,  that  is,  the  removal  of  the 
brown  sirup  still  adhering  to  it.    This  is  done, —  &),  by 
redissolving  the  raw  sugar  in  a  little  water;  6),  by  fil- 
tering the  brown  solution  through  coarsely-ground  ani- 
mal charcoal,  which  retains  the  coloring  matter  ;   c),  by 
evaporating   the   clarified    solution   in   vacuum    pans. 
The   concentrated   sirup  is  then   allowed   to   cool   in 
moulds  of  a  conical  shape,  stirring  it  frequently  to  dis- 
turb  the   crystallization ;   a  solid   mass,  consisting  of 
small  fragmentary  crystals,  the  common  loaf-sugar,  is 
obtained,  from  which  the  remaining  liquid  sugar  is  re- 
moved by  letting  a  concentrated   solution  of  crystal- 
lizable    sugar   gradually  percolate  through  (liquoring). 
The  thoroughly  purified  and  glistening  white  sugar  is 
called  refined  loaf-sugar;    that   which  is  not  so  com- 
pletely clarified,  and  has  a  yellowish  tinge,  is  the  com- 
mon loaf-sugar. 

41 


482  VEGETABLE    MATTER. 

Experiment.  —  Dissolve  half  an  ounce  of  sugar  in  a 
quarter  of  an  ounce  of  hot  water ;  the  viscous  solution 
is  called  white  sirup.  If  this  solution  is  put  in  a  cup, 
and  set  aside  in  a  warm  place,  and  evaporated  slowly, 
the  sugar  will  separate  from  it,  crystallizing  in  oblique 
six-sided  prisms.  In  a  similar  manner  white  candy  is 
prepared  on  a  large  scale  from  refined 
sugar,  brown  candy  from  raw  sugar 
As  the  crystals  deposit  more  readily  on 
substances  having  a  rough  than  on  those 
having  a  smooth  surface,  fine  threads 
or  pieces  of  wood  are  stretched  across 
the  vessels  containing  the  sirup,  and  they  soon  be- 
come coated  with  crystals. 

471.  Cane-sugar,  as  already  stated,  has  a  much 
sweeter  taste  than  grape-sugar;  therefore,  when -used 
as  a  sweetening  ag£nt,  it  possesses  a  far  greater  value 
than  the  latter.  The  white  sugar  now  occurring  in  the 
market  in  Germany  is  frequently  found  to  be  composed 
partly  or  entirely  of  starch-sugar. 

Experiment.  —  Put  into  a  test-tube  a  piece  of  cane- 
sugar,  and  into  another  some  granules  of  grape-sugar 
taken  from  a  raisin,  and  pour  over  them  strong  sul- 
phuric acid ;  the  cane-sugar  becomes  black  by  gentle 
heating  (it  is  charred),  but  not  so  the  starch -sugar.  An 
opposite  reaction  takes  place  when  the  two  sorts  ol 
sugar  are  heated  with  a  solution  of  potassa ;  the  grape- 
sugar,  but  not  the  cane-sugar,  assumes  a  dark  color. 

Experiment.  —  These  two  sorts  of  sugar  may  be 
more  accurately  distinguished  from  each  other  by  the 
copper  test.  First  add  to  the  solutions  of  sugar  some 
drops  of  a  solution  of  blue  vitriol,  then  some  drc.ps  of  a 
solution  of  potassa,  and  place  both  vessels  in  hot 
water;  the  liquid  containing  the  grape-sugar  assumes 


SUGAR.  483 

in  a  few  minutes  a  reddish-yellow  color,  while  that 
containing  the  cane-sugar  remains  blue.  The  grape- 
sugar  is  able  to  abstract  from  the  oxide  of  copper  half 
of  its  oxygen,  whereby  reddish-yellow  suboxide  of  cop- 
per is  formed  (§  354) ;  cane-sugar  is  also  able  to  effect 
this  change,  but  liot  till  after  boiling,  or  after  standing 
several  days.  The  sugar  is  converted  by  the  oxygen 
taken  up  into  an  entirely  new  substance,  called  formic 
acid.  Grape-sugar  may  be  distinctly  recognized  b} 
this  test,  even  in  an  extremely  diluted  solution. 

472.  Liquid  Sugar.  —  By  this  very  indefinite  name 
are    commonly   designated   all   those   kinds   of   sugar 
which  do  not  yield  on  evaporation  a  solid  crystalline 
or  granular,  but  a  vitreous  amorphous  mass,  which  on 
exposure  to  the  air  again  attracts  water,  and  deliques- 
ces,   ^his  kind  of  sugar  is  commonly  called  sirup  and 
molasses. 

473.  Sugar  of  milk  is  that  particular  kind  of  sugar 
which   occurs  in   milk,  and  imparts  to  it  its  agreeable 
sweetish  taste.     It  is  obtained  in  hard,  white,  crystal- 
line masses,  by  evaporating  the  sweet  whey.     Sugar  of 
milk  is  much  less  sweet  to  the  taste  than  grape-sugar, 
and  requires  six  parts  of  cold  water  for  its  solution.     It 
is  well  known  that  milk  becomes  sour  by  standing  for 
some  days ;  this  is  owing  to  the  sugar  of  milk  being 
gradually  converted  into  a  peculiar  acid,  called  lactic 
acid. 

474.  Mannite  is  a  substance  resembling  sugar,  consti- 
tuting the  principal  part  of  manna  (the  concrete  sweet 
juice  of  some  species  of  the  ash,  growing  principally  in 
Italy). 


184 


VEGETABLE    MATTER. 


CHANGES    OF    SUGAR. 


475.  a.)  Change  by  Heat.  —  Experiment.  —  Boil  in  a 
dish  half  an  ounce  of  sugar  with  one  dram  of  water, 
until  the  viscous  solution  begins  to  assume  a  yellowish 
tinge ;  then  pour  it  upon  a  plate  previously  smeared 
with  a  little  olive-oil.  The  transparent  brittle  mass  is 
melted  sugar  in  an  amorphous  state  (barley-sugar  or 
bonbons).  The  sugar  is  first  dissolved  by  water  ;  on 
boiling,  the  water  is  again  evaporated,  and  the  sugar 
passes  gradually  from  the  dissolved  to  the  melted  state. 
The  yellowish  color  indicates  that  ail  the  water  has 
passed  off',  and  that  the  sugar  is  on  the  point  of  becom- 
ing burnt. 

If  the  transparent  sugar  is  kept  for  some  weeks,  it 
becomes  opaque  and  crystalline,  when  it  can  easily  be 
broken  up  and  finely  comminuted.  There  is  a  scientific 
interest  in  this,  as  it  clearly  affords  another  illustration 
(§  280)  of  the  fact,  that,  even  in  a  solid  state,  the  small- 
est particles  of  sugar  (its  atoms)  can  change  their  sit- 
uation with  respect  to  each  other. 

Experiment.  —  Repeat  the  former  experiment,  but 
without  stopping  the  heating  on  the  appearance  of  the 
yellow  color ;  the  sugar  will  grow  darker,  until  it  finally 
attains  a  brownish-black  color,  and  will  exhale  at  the 
same  time  a  peculiar  empyreumatic  odor.  On  cooling, 
it  is  obtained  as  a  hard,  almost  black  mass,  which  soon 
deliquesces  in  the  air,  forming  a  dark  sirup,  and  is 
called  burnt  sugar  or  caramel.  A  couple  of  drops  of  it 
impart  to  a  large  vessel  filled  with  water  the  appear- 
ance of  Jamaica  rum.  On  account  of  its  strong  color- 
ing properties,  burnt  sugar  is  much  used  for  imparting 
to  liquors  —  vinegar,  alcohol,  &c.  —  a  yellow  or  brown 
color. 


SUGAR.  483 

Experiment.  —  When  exposed  to  a  still  stronger  heat, 
(he  sugar  becomes  charred,  and  finally  barns  up  like 
wood,  as  may  easily  be  seen  by  holding  a  piece  of  it 
on  a  platinum  foil  over  an  alcohol  rlarne.  The  flame 
indicates  also  that  inflammable 
gases  are  evolved.  Pure  sugar 
leaves  no  residue.  If  it  con- 
tains lime,  white  ashes  remain 
behind  upon  the  foil,  which  do 
not  volatilize  even  at  the  strong- 
est heat. 

476.  b.)  Change  by  Acids.  —  Experiment.  —  If  you 
add  a  few  drops  of  lemon-juice,  or  a  little  tartaric  acid, 
to  a  thick,  boiling  solution  of  sugar,  it  immediately  be- 
comes a  thin  liquid,  which  does  not  crystallize  on  evap- 
oration ;•  thus  is  explained  why  the  sweet  juices  of  fruits, 
in  which  organic  acids  are  always  present,  do  not  yield, 
on  being  boiled  down,  a  solid  sugar,  but  only  a  thick 
sirup.  If  you  treat  the  solution  of  sugar  as  directed  in 
the  copper  test  (§  471),  you  will  find  that  it  now  con- 
tains grape-sugar ;  cane-sugar  is  therefore  converted  by 
boiling  with  organic  acids  into  grape-sugar.  This  met- 
amorphosis is  produced  also  in  various  other  ways,  as 
by  mere  prolonged  boiling  of  the  solutions  of  sugar,  by 
boiling  them  with  diluted  sulphuric  acid,  by  fermenta- 
tion, &c.  If  sugar  is  boiled  for  a  long  time  with  diluted 
sulphuric  acid,  it  finally  passes  into  a  brown  substance, 
resembling  humus.  When  boiled  with  nitric  or  other 
acids,  which  yield  oxygen,  it  oxidizes  first  into  sac- 
charic acid,  then  into  oxalic  acid,  and  finally  into  car- 
bonic acid  and  water. 

Sugar,  as  though  it  were  an  acid,  can  combine  in 
fixed  proportions  with  oxide  of  lead,  lime,  and  many 
other  bases  ;  but  it  thereby  loses  its  sweet  taste. 
41* 


486  VEGETABLE    MATTER. 


RETROSPECT  OF  THE  VEGETABLE  MATTER  HITHERTO 
CONSIDERED  (VEGETABLE  TISSUE,  STARCH,  GUM, 
MUCUS,  AND  SUGAR). 

1.  Organic  substances  are  such  chemical  combinations 
as  are  formed  in  animals  and  vegetables  during  life. 

2.  But  we  also  designate  by  this  term  those  chemical 
combinations  which  are  formed  from  animal  and  vege- 
table  matter,  whether   they  are   transformed  with  or 
without  artificial  assistance  (products). 

3.  Organic  matter  undergoes  decomposition  with  re- 
markable facility.     We  observe  such  changes, — 

a.)  In  living  animals  and  plants  (germination,  ripen- 
ing, &c., —  respiration,  digestion,  &c.). 

b.)  In  dead  animals  and  vegetables  (fermentation, 
putrefaction,  decay,  &c.). 

c.)  In  the  decay  of  animal  and  vegetable  matter 
(charring,  burning,  &c.). 

d.)  In  the  treatment  of  organic  substances  with  acids, 
bases,  &c. 

4.  In  all  these  changes,  the  form  only  of  the  organic 
body  disappears;  the  elements   of  which  they  consist 
are  unchangeable ;  they  vanish  from  our  sight  only  be- 
cause they  assume  an  aeriform  shape. 

5.  We  have  not  yet  succeeded  (with  a  few  unim- 
portant exceptions)  in  preparing"  and  imitating'  the  or- 
ganic combinations  by  putting  together  their  constit- 
uent parts;  we  are  only  able  to  decompose  them,  and  to 
convert  the  elements  into  new  bodies. 

6.  The  four  organogens,  oxygen,  hydrogen,  carbon, 
and  nitrogen,   are  the  principal  constituents  (the  ele- 
mentary constituents)   of  all   that  lives  and  has  ever 
lived.     A  few  inorganic  substances  only  are  added  to 
them,  as  sulphur,  phosphorus,  potassium,  calcium,  &c. 


RETROSPECT. 


487 


7.  These  four  organogens  have  the  power  of  com 
bining  in  an  unlimited  manner  with  each  other,  and, 
indeed,  not  only  with  each  other,  but  also  with  many 
inorganic  substances ;  the  number  of  the  organic  com- 
binations is  therefore  almost  infinite. 

8.  Thus,  since  the  difference  of  organic  matter  can- 
not, as  in  inorganic  substances,  consist  in  the  number 
of  the  constituents,  so  the  cause  of  this  difference  must 
be  sought  for  in  the  varied  juxtaposition  or  grouping 
of  these  constituents  (compound  radicals). 

9.  Vegetable  tissue,  starch,  gum,  mucus,  and  sugar  are 
among  the  most  widely  diffused  of  the  groups  of  atoms 
(or  proximate  constituents)  occurring  in  the  vegetable 
kingdom.     They  are  present  in  all  plants. 

10.  They  have  neither  acid  nor  basic  properties,  and 
are  therefore  called  indifferent  vegetable  bodies. 

11.  There  is  a  very  great  similarity  in  their  consti- 
tution ;  namely,  they  consist   of  only  three   elements, 
carbon,  hydrogen,  and  oxygen  (they  are  non-azotized) ; 
and,  moreover,  they  contain  oxygen  and  hydrogen  al- 
ways in  the  same  proportions  as  in  water,  namely,  in 
equal  atoms. 

12.  These  four  proximate  constituents  of  the  vege- 
table kingdom  form  a  principal  ingredient  of  all  our  veg< 
etable  food;  they  perform,  accordingly,  a  very  impor 
tant  part  in  the  process  of  animal  life. 


488  VEGETABLE    MATTER. 


V.   ALBUMINOUS    SUBSTANCES   (AZOTIZED 

AND  SULPHURIZED  SUBSTANCES). 

ALBUMEN,    CASEINE,    AND    GLUTEN. 

477.  UNDER  the  head  of  Vegetable  Tissue,  when 
speaking  of  the  preparation  of  starch,  it  has  already 
been  shown  what  is  to  be  understood  by  vegetable  al- 
bumen, caseine,  and  gluten,  and  that  all  plants  contain 
in  their  juice  one  or  more  of  these  azotized  substances. 

Vegetable  albumen  is  soluble  in  water,  but  is  rendered 
insoluble  by  boiling  (it  coagulates).  It  is  found  partic- 
ularly abundant  in  culinary  plants  and  in  oily  seeds, 
as  in  almonds,  rape-seed,  flax-seed,  poppy  seeds,  &c. 

Vegetable  caseine  is  likewise  soluble  in  water,  yet  it 
does  not  coagulate  by  heat,  though  it  does  by  adding 
an  add  to  a  solution  of  it.  The  leguminous  plants, 
such  as  peas,  beans,  lentils,  &c.,  are  very  rich  in  it. 

Gluten  (vegetable  fibrine)  is  insoluble  in  water,  and 
forms  an  essential  part  of  wheat. 

Experiment.  —  Add  to  one  dram  of  bruised  peas  half 
a  dram  of  caustic  potassa  and  one  ounce  of  water,  and 
boil  the  mixture  till  a  drop  of  the  liquid  causes  a  brown 
spot  on  lead-paper  (paper  which  has  been  moistened 
with  a  solution  of  sugar  of  lead).  The  dark  color  pro- 
duced on  the  lead-paper  is  owing  to  the  formation  of 
sulphuret  of  lead ;  it  indicates  that  sulphur  from  the  peas 
has  been  rendered  soluble  by  the  potassa.  By  now 
adding  a  few  drops  of  sulphuric  or  muriatic  acid  to  the 
liquid,  the  presence  of  the  sulphur  also  makes  itself 
known  by  the  smell,  since  sulphuretted  hydrogen  gas  is 
evolved  (§  213).  Vegetable  albumen  and  gluten,  when 
thus  treated,  give  rise  to  the  same  phenomena.  The 
tarnishing  of  silver  spoons  on  remaining  for  some  time 


ALBUMEN.  y 

in  boiled  peas,  &c.,  is  now  simply  explained,  as  sul- 
])huret  of  silver  has  been  formed  on  the  surface.  Veg- 
etable albumen  (likewise  animal  albumen)  contains, 
besides  sulphur,  a  small  quantity  of  phosphorus. 

The  albuminous  substances  have  also  been  called 
proteine  substances,  because  it  was  assumed  that  a 
common  fundamental  body  (an  organic  radical)  was 
contained  in  them,  to  which  the  name  proteine  was 
given. 

478.  It  has  been  ascertained  by  careful  experiments, 
that  the  chief  proximate  constituents  of  animal  matter 
have  the  same  constitution  as  the  albuminous  substan- 
ces of  the  vegetable  kingdom,  and  this  has  led  to  the 
conclusion,  that  the  component  parts  of  the  bodies  oi 
those  animals  whose  food  consists  entirely  of  vegeta 
bles  are  derived  from  these  albuminous  substances. 
This  conclusion  is  most  fully  confirmed  by  the  consti- 
tution of  the  blood,  the  component  parts  of  which  are 
albuminous  matter  (albumen  and  animal  fibrine).  Now. 
as  the  blood  is  the  medium  of  nourishment,  the  blood 
being  first  formed  from  the  food,  and  afterwards  all  the 
other  parts  of  the  animal  body  from  the  blood,  so  we 
may  fairly  infer  that  from  the  albumen,  caseine,  and 
gluten  which  we  receive  in  the  form  of  bread,  peas,  &c., 
the  albuminous  substances  of  the  blood  are  formed 
and  from  these  the  other  parts  of  the  body.  For  this 
reason,  articles  of  food  are  esteemed  nutritive  nearly 
in  proportion  to  the  amount  of  nitrogen  they  contain. 


CHANGE  OF  ALBUMINOUS  SUBSTANCES  BY  DECAY 
AND  PUTREFACTION. 

479.    Formation    of  Ammonia.  ~  Experiment.  —  Put 
some  gluten,  some  coarse  meal,  or  some  peas,  into  a 


490  VEGF.TAP.LE  MATTER. 

Husk,  pour  in  some  water,  and  connect  the  flask  by 
means  of  a  glass  tube  with  a  second  flask,  filled  about 
an  inch  deep  with  water,  and  let  them  remain  in  a 
moderately  warm  place.  Insert,  also,  between  the  cork 
and  the  neck  of  the  first  flask,  a  strip  of  lead-paper,  in 
such  a  manner  that  part  of  it  shah1  hang  down  into  the 
flask.  The  following  changes  will  be  observed  to  take 
place,  more  rapidly  at  a  warm,  more  slowly  at  a  cold 
temperature :  — 

a.)  Bubbles  of  gas  escape  from  the  glass  tube  into  the 
second  flask ;  they  consist  of  carbonic  acid  (and  some 
hydrogen),  as  may  be  seen  by  the  turbidiiess  which 
follows  on  the  addition  of  lime-water. 

b.)  The  lead-paper  is  colored  dark,  a  sign  of  sulphuret- 
ted hydrogen  being  generated. 

c.)  A  pungent  smell  of  ammonia  is  evolved  from  the 
liquid  standing  over  the  gluten,  when  it  is  heated  with 
lime  or  potassa ;  consequently  ammonia  has  also  been 
formed. 

If  we  compare  this  process  of  decomposition  with 
that  which  takes  place  on  the  putrefaction  of  non-azo- 
tized  substances  (§445),  we  shall  observe  the  following 
principal  difference  in  the  result:  —  On  the  putrefaction 
a  '  .ilbuiiiinous  substances^  their  nitrogen  and  sulphur  (ana 
pltosphorus)  combine  with  hydrogen^  forming  ammonia 
sulphuretted  hydrogen  (and  phosphuretted  hydro- 
gen). These  aeriform  substances  are  the  chief  cause  of 
the  very  disagreeable  odor  which  is  given  off  during  the 
decay  or  putrefaction  of  azotized  substances,  —  for  in- 
stance, animal  substances.  During  the  progress  of  this 
decomposition,  there  is  formed  also,  as  in  ligneous  fibre 
a  brown  substance  resembling  humus.  - 

However  disgusting  may  be  the  products  of  putrefac- 
tion and  decay,  they  nevertheless  contain  within  them 


ALBUMEN.  i 

belves  the  germ  of  the  most  beautiful  compounds  ;  the 
most  beautiful  plants  arise  from  such  products  of  de- 
cay. Indeed,  the  most  nauseous-smelling  decaying 
azotized  substances  are  the  most  powerful  means  of 
rendering  our  fields  and  gardens  fertile  (the  best  ma- 
nures). 

480.  Formation  of  Nitre.  —  Experiment.  —  Mix  some 
flax-seed  meal  with  wood-ashes,  sand,  and  lime,  and  let 
this   mixture   remain   exposed   to   the    air   for    several 
months  in  the  summer  season,  frequently  moistening  it 
with  water,   and  stirring  it.      If  the  mixture  is  then 
treated  with  hot  water,  and  the  solution   evaporated, 
prismatic  crystals  will  be  formed  from   the  latter  on 
cooling,  which  will  detonate  smartly  when  thrown  upon 
glowing  coals ;  they  consist  of  nitre  (§  207). 

Here,  also,  ammonia  is  in  the  first  place  formed 
from  the  nitrogen  of  the  vegetable  albumen,  present  in 
great  abundance  in  the  flax-seed  meal ;  but  it  is  induced 
by  the  predisposing  influence  of  the  strong  base  to  un- 
dergo still  further  putrefaction,  that  is,  to  attract  oxygen 
from  the  air,  whereby  water  is  formed  from  its  hydro- 
gen, and  nitric  acid  from  its  nitrogen,  the  latter  of 
which  combines  with  the  potassa  and  lime. 

From   ammonia  =     N          H3 
and  oxygen          =     O5         O3 
are  formed  nitric  acid  and  water  =  N  O5  -f-  3  H  O. 

In  a  similar  manner  nitre  is  often  generated  in  arable 
land,  whence  it  passes  into  the  juice  of  plants;  thus  it 
is  known  that  beets  and  tobacco  growing  upon  very 
strongly  manured  soil,  and  also  those  rank  plants  grow- 
ing on  manure-heaps,  such  as  henbane,  thorn-apples, 
&c.,  are  frequently  so '  rich  in  nitre,  that  when  dried 
they  emit- sparks,  if  burnt  on  charcoal. 

481.  The  extraordinary  facility  with  which  albumi 


492  VEGETABLE     MATTER. 

nous  substances  undergo  decomposition^  when  they  are 
exposed  to  the  air  in  the  moist  state,  is  explained  very 
simply  by  the  fact  that  they  contain  five,  indeed,  six  ele- 
ments, and  always  several  atoms  of  each,  as  component 
parts  (§§  425,  429).  If  during  their  decomposition  they 
come  in  contact  with  non-azotized  substances,  these  al 
so  are  induced  to  enter  into  decomposition,  —  they  are, 
as  it  were,  infected.  There  follows  in  this  connection 
that  important  change  which  sugar  experiences  when  it 
is  brought  in  contact  with  albuminous  substances  in  a 
state  of  decomposition.  This  metamorphosis,  known 
under  the  name  of  spirituous  fermentation,  will  be  more 
particularly  considered  in  the  following  pages. 

RETROSPECT    OF   THE   ALBUMINOUS  SUBSTANCES    (AL- 
BUMEN,   CASE1NE,    GLUTEN). 

1.  The  albuminous  substances  are  characterized  by 
containing,  not  only  carbon,  oxygen,  and  hydrogen,  but 
also  nitrogen  and  sulphur. 

2.  On  account  of  this  complex  nature,  they  are  decom- 
posed with  the  greatest  ease  (fermentation,  putrefaction, 
decay). 

3.  If  while  they  are  decomposing  they  come  in  con- 
tact with  other  organic  substances,  they  cause  these 
also  to  enter  into  fermentation,  decay,  putrefaction,  &c. 

4.  All  vegetables  contain,  though  not  always  in  great 
quantity,  one  of  these  substances;  from  this  universal 
diffusion,  we  infer  that  it  has  an  important  office  to  dis- 
charge ; 

5.  Which  office  consists   undoubtedly  in    this,  that 
by  means  of  it  the  growth  and*  nourishment  of  plants 
may  be  brought  about. 


CONVERSION  OF  SUGAR  INTO  ALCOHOL.      493 

VI.    CONVERSION  OF    SUGAR   INTO  ALCO- 
HOL (ALCOHOLIC  FERMENTATION). 

482.  Experiment.  —  Half  an  ounce  of  honey  is  dis- 
solved in  four  .ounces  of  water,  and  some  of  the  gluten 
or  caseine  from  experiment  §  479,  in  a  state  of  decom- 
position, is  added  to  it;  the  liquid  is  then  put  in  a 
moderately  warm  place  (18°  to  24°  C.),  when  it  soon 
enters  into  fermentation,  with  the  evolution  of  a  largo 
quantity  of  gas.  If  you  perform  the  experiment  in  a 
Fig  I8g  flask  furnished  with  a 

bent  glass  tube,  one  end 
of  which  is  passed  under 
a  second  flask,  filled  with 
water,  which  is  invert- 
ed over  the  pneumatic 
trough,  the  gas  may  easi- 
ly be  collected ;  it  consists 
of  carbonic  acid.  If  the  liquid  still  retains  a  sweet  taste 
after  the  evolution  of  the  gas  has  ceased,  then  add  an- 
other portion  of  the  gluten  to  it,  whereby  the  fermenta- 
tion is  again  renewed.  Finally,  all  the  saccharine  taste 
will  have  disappeared,  and  the  liquid  will  have  ac- 
quired a  spirituous  flavor.  The  fermented  liquor  is 
called  metheglin;  instead  of  sugar  it  contains  alcohol, 
and  this  is  the  reason  of  its  intoxicating  effect.  A  por- 
tion of  the  gluten  is  found  at  the  bottom  of  the  vessel, 
converted  into  a  brownish  residue. 

All  albuminous  matter  in  a  state  of  decomposition, 
as,  for  instance,  old  cheese,  putrefying  flesh,  blood,  &c., 
acts  like  putrefying  gluten;  but  the  substance  which 
possesses  this  fermenting  power  in  the  highest  degree  is 
the  altered  gluten  of  barley,  obtained  in  great  quan- 
42 


494 


V^F, r; r. T A u i.r.   M A TT E R. 


tity  as  a  secondary  product  in  the  brewing  of  beer  (sur- 
face yeast,  or  brewers  yeast).  All  substances  which 
are  able  to  excite  fermentation  in  solutions  of  sugar  are 
designated  by  the  term  ferment.  Surface  yeast  (§488) 
is  accordingly  the  most  powerful  ferment. 

Experiment.  —  Repeat  the  former  experiment,  adding, 
instead  of  the  gluten,  a  teaspoonful  of  yeast  to  the 
honey-water ;  the  process  of  fermentation  will  now  pro- 
ceed much  more  rapidly  and  regularly. 

483.  The  change  which  the  sugar  experiences  during 
this  process  may  be  rendered  very  intelligible  by  com- 
paring together  the  formulas  of  sugar,  alcohol,  and  car- 
bonic acid. 

1  atom  of  honey  or  grape-sugar  consists  of  C6  O6  H6 ; 
from  this  are  formed  1  atom  of  alcohol  =  C4  O^  H6, 

and  2  atoms  of  carbonic  acid  =  C2  O4  =  2C  O2. 

Alcohol  and  carbonic  acid,  added  together,  yield 
again  the  constituents  of  sugar.  Thus  sugar  is  resolved 
by  fermentation  into  alcohol  and  carbonic  acid. 

Fig.  189. 


Grape  sugar. 


Alcohol. 


Carbonic  acid. 


Both  substances  did  not  previously  exist  in  the  sugar, 
but  they  are  new  products  of  a  peculiar  decomposition 
of  the  sugar,  —  peculiar  for  this  reason,  that  they  are 
exclusively  made  up  of  the  elements  of  the  sugar, 
without  any  thing  being  either  subtracted  from  it  or 
added  to  it.  The  ferment  works  also  in  the  same  pe- 
culiar manner ;  it  induces  a  decomposition  of  the  sugar, 
yet  without  combining  with  the  sugar,  taking  any 


CONVERSION    OF    SUGAR    INTO    ALCOHOL.  495 

thing  from  it,  or  giving  any  thing  to  it;  its  mode  of 
operation  is  analogous  to  that  of  sulphuric  acid,  when 
the  latter  converts  starch  into  sugar  (§  459).  The  acT 
tion  of  the  ferment,  however,  differs  from  that  of  sul- 
phuric acid  just  alluded  to,  since  the  ferment  itself  does 
no1  remain  unchanged,  but  is  also  decomposed  during 
the  fermentation.  Accordingly,  two  sorts  of  changes 
are  going  on  by  the  side  of  each  other  in  the  fermenting 
liquids;  —  1.)  that  of  the  azotized  ferment;  2.)  that  of 
the  non-azotized  sugar.  The  ferment  always  commen- 
ces the  change,  which  is  continued  in  the  sugar,  as  if 
the  latter  were  infected.  The  process  is  very  similar 
to  what  occurs  in  the  case  of  a  fresh  apple,  which  be- 
gins to  rot  on  coming  in  contact  with  one  already  in 
the  act  of  rotting. 

Experiment.  —  Instead  of  honey,  take  a  solution  of 
white  sugar,  and  add  some  yeast  to  it ;  in  this  case  the 
fermentation  will  not  take  place  so  soon,  since  the  cane- 
sugar  must  pass  into  grape-sugar  before  its  decom- 
position into  alcohol  and  carbonic  acid  can  commence. 
This  transition  takes  place  simply  by  the  addition  of 
one  atom  of  water;  for  if  one  atom  of  water  is  added 
to  the  cane-sugar,  =  C6  H  O5,  there  is  formed  Cs  IT6  O6, 
or  grape-sugar. 

WINE. 

184.  All  sweet  vegetable  juices  pass  spontaneously 
into  fermentation  without  the  necessity  of  adding  to 
them  a  ferment,  because  they  always  contain  sugar  and 
one  of  the  albuminous  substances,  as  albumen,  caseine, 
or  gluten. 

Experiment.  — Submit  freshly  expressed  beet-juice  to 
a  temperature  of  about  20°  or  25°  C. ;  the  juice  will 


496  VEGETABLE    MATTER. 

soon  effervesce,  deposit  a  sediment,  and  be  converted 
into  a  spirituous  liquid  (beet-wine). 

In  the  same  manner  currant  and  gooseberry  wines 
are  prepared  from  currants  and  gooseberries,  cider  from 
apples,  the  so-called  cherry-water  by  fermenting  and 
afterwards  distilling  the  cherry-juice,  rum  by  ferment- 
ing and  afterwards  distilling  the  juice  of  the  sugar- 
cane, &c. 

The  most  common  of  all  the  fermentations  of  this 
kind  is  the  fermentation  of  the  grape-juice,  wine  being 
the  result.  In  order  to  prepare  clear  wine,  the  grapes 
are  pressed,  the  juice  (must)  is  poured  into  vats  and  al- 
lowed to  remain  in  them  in  the  cellar,  where,  as  the 
temperature  is  tolerably  low,  the  fermentation  proceeds 
so  slowly  that  it  is  not  completed  until  after  some 
months.  The  young  wine  is  racked  off  from  the  lees, 
and  poured  into  fresh  vats  ;  it  still  contains  a  small 
quantity  of  sugar  and  albuminous  matter,  which  are 
both  gradually  converted,  the  former  into  alcohol  and 
carbonic  acid,  the  latter  into  lees  (after  fermentation). 
In  the  manufacture  of  red  wine,  the  purple  grapes  are 
bruised,  and  then  fermented,  together  with  their  skins 
and  stalks  ;  a  red  coloring  matter  is  extracted  from  the 
skins,  and  tannin  from  the  stalks  and  seeds,  the  tannin 
imparting  to  this  species  of  wine  its  favorite  astringent 
taste.  Sparkling  wine  (Champagne)  is  made  by  letting 
the  fermentation  proceed  in  corked-up  bottles,  whereby 
the  carbonic  acid  formed  is  retained  in  the  wine. 

485.  The  grapes  growing  in  northern  countries,  for 
instance,  in  Germany,  contain  proportionably  more 
albuminous  matter  and  tartar  than  sugar,  which  ac- 
counts for  the  difference  in  the  smell  and  taste  of  wine. 
The  taste  of  the  German  wines  is  not  sweet,  because 
the  albuminous  substances  present  are  more  than  suffi 


CONVERSION  OF  SUGAR  INTO  ALCOHOL.      497 

cient  to  decompose  all  the  sugar ;  the  odor  (the  flower 
or  the  bouquet)  is  peculiarly  pleasant,  because,  the  tartar 
being  abundant,  there  is  generated  during  the  fermen- 
tation a  volatile  substance  (oenanthic  ether))  which  pos- 
sesses a  very  agreeable  odor. 

It  is  different  with  the  grapes  of  the  more  southern 
countries,  as  Greece,  Spain,  Portugal,  &c.  Here,  in 
consequence  of  the  higher  temperature,  the  grapes  are 
richer  in  sugar,  but  poorer  in  tartar  and  albuminous 
matter.  In  this  case  the  latter  substance  is  not  suffi- 
cient to  effect  the  decomposition  of  all  the  sugar  during 
the  fermentation,  so  that  a  part  of  the  sugar  remains 
vmdecomposed,  and  gives  to  the  wine  a  sweet  taste. 
Neither  is  any  oenanthic  ether  generated,  since  the  due 
quantity  of  tartar  is  wanting;  consequently  these  wines 
possess  no  bouquet. 

486.  Experiment.  —  If  some  wine  is  put  into  a  retort, 

and  subjected  to 

Fig'190'  distillation    at   a 

moderate  heat,  at 
first  the  more 
volatile  alcohol, 
together  with  the 
oenanthic  ether, 
will  pass  over. 
A  very  agreeable 
smelling  spirit  is 

thus  obtained,  known  in  commerce  under  the  name  of 
Cognac,  or  French  brandy.  In  the  wine  countries,  the 
lees  remaining  after  the  wine  is  racked  off  are  general- 
ly used  for  this  purpose,  since,  in  the  swollen,  pap-like 
state  into  which  they  settle  in  the  vats,  they  retain  me* 
shanically  a  large  quantity  of  wine. 

42* 


498  VEGETABLE  MATTER. 

BEER. 

487.  Next  to  wine,  beer  and  brandy  are  the  most  im« 
portant  fermented  liquors.  The  manufacture  of  them 
differs  essentially  from  that  of  wine  in  this  respect ; 
that  materials  are  employed  which  contain  no  sugar 
already  formed,  but  instead  of  it  starch,  such  as  barley, 
wheat,  rye,  potatoes,  &c.  Starch  cannot,  like  sugar,  be 
resolved  directly  into  alcohol  and  carbonic  acid ;  and, 
when  employed  in  the  manufacture  of  alcohol,  it  must 
previously  be  converted  into  sugar.  This,  in  the  pres- 
ent case,  is  always  effected  by  the  diastase  of  the  bar- 
ley-malt in  the  so-called  mashing  process  of  the  brewers 
and  brandy-distillers  (§  461). 

Experiment.  —  Pour  a  mixture  of  an  ounce  and  a 
half  of  cold  water  and  two  ounces  of  boiling  water 
upon  half  an  ounce  of  bruised  malt,  and  set  it  aside  for 
some  hours  in  a  warm  place,  where  it  will  reach  a  tem- 
perature of  about  65 3  or  75°  C. ;  a  sweet  liquid  is 
thus  obtained,  composed,  not  only  of  dextrine  and  sugar, 
but  containing  also  the  gluten,  thereby  rendered  soluble, 
which  was  present  in  the  malt.  The  brewer  calls  this 
liquid  the  wort.  Strain  it  with  pressure  through  a 
cloth,  and  boil  the  liquid  for  some  time,  until  it  becomes 
clear  and  transparent ;  then  let  it  cool  to  30°  C.,  and  add 
to  it  a  teaspoonful  of  yeast ;  it  will  soon  begin  to  fer- 
ment, and  after  some  days  will  clarify  again ;  the  clear, 
fermented  liquor  is  beer.  This  is  the  mode  of  making 
the  Berlin  white  or  pale  beer,  which  is  not  bitter.  If 
during  the  boiling  some  hops  (female  flowers  of  the  hop- 
vine)  are  added  to  the  wort,  an  aromatic  bitter  substance 
is  dissolved  from  them  (lupuliri),  which  not  only  imparts 
to  the  beer  a  pleasant  and  bitter  taste,  but  also  a  great 
er  body. 


CONVERSION  OF  SUGAR  INTO  ALCOHOL.      499 

488.  What  is  particularly  remarkable  in  the  above 
fermentation  (superficial  fermentation)  is  the  great  quan- 
tity of  yeast  that  separates.  It  proceeds  from  the  glu- 
ten of  the  barley,  which  is  dissolved  during  the  mashing 
process,  but  in  the  course  of  the  fermentation  is  again 
precipitated  as -insoluble  yeast.  This  is  called  surface 
yeast,  it  being  raised  to  the  surface  in  consequence 
of  the  great  evolution  of  carbonic  acid,  and  when 
the  vats  are  full,  it  is  caused  to  pass  out  through  the 
bunghole ;  it  is  the  best  ferment,  and  the  quantity  ob- 
tained in  the  last  experiment  is  sufficient  to  bring  to 
complete  fermentation  the  wort  of  a  whole  pound  of 
malt.  Its  power  of  exciting  fermentation  is  destroyed 
when  it  is  rendered  quite  dry,  or  when  it  is  boiled,  or 
very  finely  triturated;  and  likewise  by  mixing  antisep- 
tic substances  with  it,  as,  for  instance,  alco- 
JJQ^  pyroligneous  acid,  sulphurous  acid,  vola- 
tile oils,  &c.  This  yeast,  when  examined 
through  the  microscope,  has  exactly  the 
form  of  simple  vegetable  cells  (a) ;  and  their 
increase  in  the  wort  takes  place  in  the  same 
manner  as  in  the  most  simple  plants,  new  cells  or  buds 
developing  themselves  on  each  globule  of  the  old  yeast. 
These  globules  are  hollow,  filled  with  an  azotized 
liquid,  to  which  is  to  be  ascribed  the  power  of  the 
yeast  to  excite  fermentation. 

New  beer  holds,  also,  some  sugar  and  gluten  in  solu- 
tion; iherelbre,  like  wine,  it  undergoes,  when  kept,  a 
second  slight  fermentation  (after-fermentation).  If  this 
is  allowed  to  take  place  in  well-stopped  bottles,  so  that 
the  carbonic  acid  cannot  escape,  a  foaming  beer  (bottled 
beer)  is  obtained,  in  the  same  way  as  in  the  manufac- 
ture of  sparkling  Champagne. 

But  all  the  gluten  is  not  separated,  even  by  the  see* 


500  VEGETABLE    MATTER. 

ond  fermentation,  and  hence  the  upper  fermenting 
(light)  beer  undergoes  a  still  further  change  on  being 
exposed  to  the  air ;  it  is  the  alcohol,  however,  which  is 
now  altered  by  the  albuminous  matter  undergoing  de- 
composition ;  it  passes  into  vinegar,  and  the  beer  be- 
comes acid. 

489.  Experiment.  —  Repeat   the   former   experiment, 
but  cool  the  wort  below  10°  C.  before  adding  the  yeast, 
and  then  let  the  liquid  remain  in  a  cool  place  ;  a  very 
gradual  fermentation  takes   place,  which  will  not  be 
concluded    for    several    weeks,    perhaps    even    months. 
During  this  process,  the  carbonic  acid  is  evolved  in  very 
small  bubbles,  and  the  yeast  settles  at  the  bottom  of 
the  vessel  (sediment  ferment,  bottom  yeast).     The  beer 
thus  prepared  contains  scarcely  a   trace   of  gluten  or 
yeast,  and  therefore  can  be  kept  for  years  without  be- 
coming sour;  it  is,  moreover,  richer  in  carbonic  acid 
than  that  obtained  by  the  superficial  fermentation  pro- 
cess, because  at  the  lower  temperature,  and  by  the  more 
gradual  elimination  of  carbonic  acid  gas,  it  was  able  to 
retain  more  of  it.    The  stronger  kinds  of  beer  (Bavarian 
beer,  strong-  beer,  &c.)  are  made  in  this  way.    The  thick 
bottom  yeast,  separating  during  this  process,  acts  in- 
deed as  an  exciter  of  fermentation  upon  the  sugar,  but 
far  more  slowly  and  gently  than  the  frothy  surface  yeast. 

490.  The  peculiarities  of  the  two  methods  of  fermen- 
tation may  be  elucidated  as  follows  :  — 

Surface  Fermentation  Bottom  Fermentation 

a.;  takes  place  at  a  higher  temper-  at     a     lower     temperature      (5- 

ature  (12-20°  C.) ;  10°  C.). 

6.)  takes  place  rapidly  (in  three  or  slowly  (in  six  or  eight  weeks). 

four  clays) ; 

c.)  in  this  case  imperfect  separation  in  this  case  thorough  separation  of 

of  the  yeast  by  flowing  over ;  the  yeast  by  settling. 

d.)  surface  yeast  is  finely  divided  bottom  yeast  is  compact  and  heavy 

and  frothy ; 


CONVERSION  OF  SUGAR  INTO  ALCOHOL.      501 

* ._)  surface  yeast  is  a  strong  exciter  bottom  yeast  a  feeble  exciter  of  fer« 

of  fermentation ;  mentation. 

/!)  surface  fermented  beer  soon  be-  bottom  fermented  beer  does  noi. 
comes  sour; 

j  )  surface  fermented  beer  contains  bottom  fermented  beer  more, 
but  little  carbonic  acid  ; 

A.)  serves  for  the  manufacture  of  serves  for  the  manufacture  of  strong 

weak  beer ;  beer. 

i.)  by  lowering  the  temperature  the  by  raising  the  temperature  the 
surface  fermentation  may  be  bottom  fermentation  may  be 
converted  into  bottom  fermen-  converted  into  surface  fermen- 
tation, tation. 

Experiment.  —  Subject  a  weighed  or  measured  quan- 
tity of  beer  to  distillation  (§  486) ;  a  weak  alcohol,  to- 
gether with  carbonic  acid,  will  first  pass  over,  and  finally 
only  a  watery  liquid.  Pour  the  yet  fluid  residue  into  a 
cup,  and  set  it  in  a  warm  place  ;  it  dries  up,  forming  a 
dry  amorphous  mass  (extract  of  beer),  which  consists 
principally  of  dextrine,  sugar,  and  the  bitter  principle  of 
hops.  By  determining  the  strength  and  the  quantity  of 
the  alcohol,  and  the  weight  of  the  extract  obtained,  we 
have  the  two  most  important  factors  for  estimating  the 
nature  and  purity  of  the  beer. 

BRANDY. 

491.  The  preparation  of  brandy  is  similar  to  that  of 
beer,  inasmuch  as  substances  containing  starch  are  like- 
wise employed  in  the  preparation  of  it,  and  as  the  starch 
must  first  be  converted  into  sugar  before  the  fermenta- 
tion can  proceed.  This  is  done,  as  in  the  case  of  beer, 
by  the  mashing  process,  that  is,  by  the  operation  of  the 
diastase  of  the  malt  upon  the  starch.  To  this  end 
either  boiled  and  mashed  potatoes  or  rye  are  mixed 
with  bruised  barley-malt  and  hot  water,  so  as  to  form 
a  paste,  which  is  to  be  kept  at  a  temperature  of  70°  C 
until  a  complete  formation  of  sugar  is  effected;  theu 


502 


VEGETABLE  MATTEL. 


brewers'  yeast  (surface  ferment)  is  added  to  the  sweet 
mash  or  wort  previously  cooled  off,  whereby  fermenta- 
tion is  induced.  When  this  fermentation  is  concluded 
put  the  mass  into  a  copper  boiler,  and  distil  the  vola- 
tile alcohol  from  the  non-volatile  parts  (husks,  gluten, 
fibrous  matter,  &c.).  The  residue  is  used  as  a  nourishing 
food  for  the  fattening  of  cattle.  Formerly  simple  stills 
were  used  for  this  distillation,  and  a  thin  spirit  (brandy 
or  low  wines)  was  obtained,  which  consisted  of  about 
one  third  of  alcohol  and  two  thirds  of  water;  but  now  a 
more  complicated  apparatus  is  universally  employed,  by 
means  of  which  a  brandy  of  double  the  strength  is  ob- 
tained (rectified  spirit).  The  principle  upon  which  this 
apparatus  depends  will  be  explained  in  the  following 
experiment. 

492.  Rectification  or  Strengthening'  of  Brandy.  —  Ex- 
periment. —  Pour  three  ounces  of  common  brandy  in- 
to a  capacious  flask,  and  carefully  distil  half  of  it 
into  a  vessel,  which  is  cooled  by  means  of  very  cold 
water,  or  what  is  still  better,  by  ice.  If  the  brandy 

Fig  192. 


contained  thirty  per  cent,  of  spirit,  then  the  ounce  ana 
*  half  of  alcohol,  first  passing  over,  will    contain   at 


CONVERSION    OF    SUGAR    INTO    ALCOHOL. 


503 


jeast  fifty  per  cent.  Alcohol  is  more  volatile  than 
water,  therefore  it  first  passes  over,  in  company  with  a 
smaller  quantity  of  the  latter,  while  the  larger  quantity 
of  the  water,  together  with  the  fusel  oil  which  might 
have  been  contained  in  the  brandy,  remains  behind  in 
the  flask  (phlegm). 

493.  Experiment.  —  If  you  connect  with  the  flask 
and  the  receiver  an  intermediate  vessel,  a  wide-mouthed 
vial,  for  instance,  which  is  easily  done  by  means  of 

Fig.  193. 


two  glass  tubes  bent  at  right  angles,  and  a  cork  perfo- 
rated with  two  holes,  and  then  repeat  the  above  ex- 
periment of  distillation,  the  alcohol  vapors  passing  over 
will  first  condense  in  the  middle  vessel.  But  as  this 
vessel  is  not  cooled  down,  the  liquid  condensed  in  it 
will  finally  also  boil,  and  the  vapors  thus  formed  will 
pass  over  into  the  receiver  surrounded  with  cold  water, 
and  will  there  be  condensed  for  the  second  time.  In 
this  manner  a  double  distillation  (rectification)  is  effect- 
ed. The  flask  contains  boiling  brandy  (at  30°  Tral- 
les*);  the  intermediate  vessel,  boiling  rectified  alcohol 

*  The  alcoholometer  of  Tralles  floats  to  a  figure  on  the  stem,  which  indi- 
cates the  percentage  of  alcohol,  by  volume,  in  the  liquor  in  which  it  is 
placed 


VEGETABLE  MATTER. 

(at  about  50°  Tralles).  After  the  termination  of  the 
experiment,  the  first  vessel  will  contain  phlegm  ;  thft 
second,  weak  spirit;  and  the  third,  very  strong  highly 
rectified  spirit  (of  70  to  80°  Tralles). 

If  you  adapt  to  the  corks  of  the  first  two  vessels  a 
couple  of  thermometers,  which  shall  dip  into  the  liquid, 
you  will  find  that  the  liquid  in  the  flask  boiled  at  the 
commencement  of  the  experiment  at  85°  C.,  and  at  the 
end  of  the  experiment  at  from  95  to  100°  C.,  while  that 
contained  in  the  second  vessel  commenced  boiling  at 
80°  C.,  and  ended  with  boiling  at  from  85°  to  90°  C. 
It  is  obvious  from  this  that  a  strong  spirit  boils  at  a 
much  lower  temperature  than  that  at  which  weaker 
spirits  boil.  The  strongest  alcohol  (absolute)  boils  at 
78°  C.,  consequently  at  twenty-two  degrees  lower  than 
water. 

494.  Experiment.  —  Connect  with  a  flask  a  tolerably 
/arge  glass  tube,'  which  is  so  bent  that  its  middle  part 
may  have  a  slight  inclination  upwards,  as  is  shown  in 
the  annexed  figure ;  from  b,  this  tube  is  wound  round 

Fig.  195. 

6 


with    moistened   wick-yarn,    the  end   of  which  hangs 
down  at  a.     At  a,  bind  a   strip   of  cloth   (several  times 


CONVERSION  OF  SUGAR  INTO  ALCOHOL. 


505 


folded  together  and  smeared  with  some  drops  of  olive- 
oil)  round  the  tube,  so  that  the  water  from  the  wick 
may  not  run  down  upon  the  flask.  Now  distil  as  be- 
fore three  ounces  of  brandy,  but  during  the  distillation 
continually  drop  cold  water  upon  the  wick-yarn,  at  6, 
in  order  to  cool  the  vapor  of  brandy  as  it  passes  over. 
Catch  the  water  running  down  the  outside  of  the  tube 
in  a  vessel  placed  below  the  end  of  the  wick-yarn. 
If  the  distillation  is  arrested  when  about  one  ounce 
of  brandy  has  passed  over,  we  shall  have  a  stronger 
spirit  in  the  receiver  than  was  obtained  in  the  experi- 
ment in  §  492,  because,  by  the  partial  cooling  of  the 
vapor  of  the  brandy,  the  principal  part  of  the  less  vol- 
atile aqueous  steam  was  condensed,  and  therefore  a 
vapor  richer  in  alcohol  passed  into  the  receiver,  while 
the  water  condensed  in  the  tube  flowed  back  into  the 
flask. 

This  principle  of  partial  refrigeration  has  been  most 
successfully  applied  to  the  distillation  of  brandy  on  a 
large  scale.  The  best-known  apparatus  used  for  this 
purpose  is  called  the  dephleg- 
mator,  and  is  so  contrived  th"at 
the  hot  vapors  rising  from  the 
still  must  pass  through  several 
copper  channels  before  reaching 
the  refrigerator;  these  channels 
have  a  division-wall  in  the  cen- 
tre, and  are  kept  cold  exter- 
nally by  a  constant  current  of 
water.  We  obtain  in  this  way 

a  spirit  of  from  70°  to  80°  Tralles,  while  a  simple  still 
yields  only  a  weak  spirit  of  30°  Tralles. 

495.  Alcohol  is  rendered  not  only  stronger,  but  purer, 
by  the  above-mentioned  rectification.     Besides  alcohol. 
43 


Fig.  196. 


506  VEGETABLE    MATTER. 

there  is  formed  from  grain  and  potatoes,  during  fer- 
mentation, an  oily,  disagreeably  smelling  liquid,  the  so- 
called  fuse  I  oil,  and  also  some  vinegar.  Both  are  less 
volatile  than  alcohol,  and  therefore,  during  the  above 
rectification,  are  for  the  most  part  condensed  with  the 
water,  which  flows  back.  The  phlegm  is  accordingly 
a  mixture  of  water  with  alcohol,  fusel  oil,  and  vinegar. 
The  alcohol  may  be  thoroughly  purified  from  the  fusel 
oil  by  letting  it  stand  for  some  time  in  contact  with 
freshly  burnt  charcoal,  and  then  filtering  it  off;  the  fusel 
oil  remains  behind  in  the  pores  of  the  charcoal  (§  105). 
It  is  still  more  advantageous  to  let  the  alcoholic  vapors, 
before  their  condensation  after  distillation,  pass  through 
a  cylinder  filled  with  charcoal,  and  applied  over  the 
dephlegmator. 

496.  In  the  same  way  that  brandy  is  made  in  Ger- 
many from    grain   and   potatoes,    a   spirituous   liquor 
called  arrack  is  prepared  in  the  East  Indies  from  rice, 
by   mashing,   fermenting,   and   distilling,   and   mixing 
with  it  the  seeds  of  the  palm-tree,  thus  imparting  to  it 
a  peculiar  flavor,  and  an  odor  resembling  that  of  rum. 

497.  All  fermented  liquors  contain  alcohol,  and  owe 
to  this  their  intoxicating  power.     The  quantity  of  it 
contained  in  our  ordinary  spirituous  liquors  is  shown 
in  the  following  table :  — 

Pure  Alcohol. 

In  100  measures  of  common  beer  are  contained     1^  —    2  measures. 

"          strong  beer,  3    —    5  " 

"          porter  or  ale,  6    —    8  " 

"          wine,  10—15  " 

"          Madeira  wine,  18—24  " 

"          French  brandy,  40    —45  " 

"          liqueur,  45    —  50  " 

"          rum  or  arrack,  50    —  60  " 

"          rectified  spirit,  60—70  " 

alcohol,  70    —75  " 

u          highly  rectified  alcohol,  86—90  u 


CONVERSION  OF  SUGAR  INTO^  ALCOHOL.      507 

SPIRIT  OF  WINE,  OR  ALCOHOL. 

498.  Anhydrous  Alcohol.  —  Alcohol  has  as  yet  only 
been  obtained  by  the  fermentation  of  sugar.  In  the 
preceding  chapters  we  have  already  shown  how  alcohol 
is  formed,  how^  it  is  rendered  stronger,  and  how  it  is 
purified.  This  is  done  by  incomplete  distillation,  or 
by  incomplete  condensation,  since  the  alcohol  is  more 
difficult  to  volatilize  than  water,  and  its  vapor  more 
difficult  to  condense  than  steam.  But  all  the  water 
cannot  be  separated  in  this  way  from  the  alcohol,  as 
the  alcohol  retains  one  tenth  part  of  the  water  so  firmly 
that  it  can  neither  be  withdrawn  from  it  by  distillation 
nor  by  cooling.  In  order  to  procure  it  absolutely  an- 
hydrous, a  body  must  be  presented  to  it  which  has  a 
greater  affinity  for  water,  and  fixes  it  so  firmly,  that  it 
cannot  evaporate  with  the  alcohol  at  the  boiling  point 
of  the  latter.  Such  a  body  is  quicklime. 

Experiment. —  Put  into  a  flask  one  ounce  of  quick- 
lime that  has  been  broken  into  small  pieces,  and  pour 
upon  it  one  ounce  of  very  strong  alcohol ;  connect  a 
receiver  with  the  flask,  as  in  the  experiment  in  §  492, 
and  let  the  mixture  remain  in  repose  for  one  day.  The 
lime  gradually  combines  with  the  water  of  the  alcohol 
(it  slakes),  and  the  latter  is  procured  anhydrous  by  dis- 
tilling it  off  at  a  moderate  heat.  The  best  method  of 
distilling  in  this  case  is  over  the  water-bath  (Fig.  88). 
Anhydrous  alcohol  is  also  called  absolute  alcohol.  In 
this  experiment,  the  vessels  used  mast  be  previously 
rinsed  out,  not  with  water,  but  with  strong  alcohol, 
because  the  moisture  adhering  to  the  vessel  would 
again  impart  water  to  the  anhydrous  alcohol. 

499.  Properties  of  Alcohol.  —  Alcohol  has  a  burning 
taste,  and  a  penetrating,  agreeable  odor.  Strong  alco- 
hol, especially  absolute  alcohol,  acts  as  a  poison  when 


508  VEGETABLE    MATTER. 

swallowed ;  but  when  diluted,  it  is,  as  is  well  known, 
stimulating  and  intoxicating. 

Strong  alcohol  has  never  been  frozen,  even  at  a 
cold  of  — 100°  C. ;  it  is  therefore  excellently  adapted 
for  the  making  of  thermometers  by  which  great  de- 
grees of  cold  are  to  be  measured.  For  this  reason  it  is 
likewise  serviceable  in  the  illuminating-gas  apparatus, 
for  preventing  in  winter  the  freezing  of  the  water  which 
settles  in  the  gas-pipes,  and  the  consequent  obstruction 
of  the  pipes.  The  illuminating  gas,  on  leaving  the  gas- 
ometers, is  first  made  to  pass  through  alcohol  before  it 
is  conducted  farther,  whereby  the  steam  is  not  only 
withdrawn  from  the  gas,  but  so  much  vapor  of  alcohol 
is  also  added  to  it,  that  the  liquid  now  condensing  in  the 
pipes  does  not  freeze  at  the  temperature  of  our  winters. 

If  common  alcohol  is  placed  in  an  open  vessel,  the  al- 
cohol evaporates  more  rapidly  than  the  water  contained 
in  it.  Strong  alcohol  may  also  attract  water  from 
the  air.  Thus  is  explained  why  all  spirituous  liquids 
must,  when  in  unclosed  vessels,  lose  strength,  and  be- 
come richer  in  water.  The  young  chemist  is  frequently 
reminded  of  this  fact  in  the  case  of  the  spirit-lamp ;  it 
will  not  burn  when  it  has  remained  exposed  to  the  air 
for  some  time  unprotected.  Why  not?  The  spirit  has 
passed  away  through  the  wick,  the  phlegm  remaining 
behind. 

The  boiling'  and  evaporation  of  alcohol  have  already 
been  treated  of  at  §§  493  and  494,  and  the  combustion 
of  it  in  §  121.  Alcohol  contains  so  little  carbon,  that 
no  soot  is  separated  during  its  combustion  ;  hence,  also, 
the  alcohol  flame  emits  but  a  feeble  light.  The  strength 
best  adapted  for  spirit  used  in  burning  is  that  from  75° 
to  80°  Tralles ;  if  weaker,  all  the  water  will  not  evapo- 
rate during  the  combustion,  and  phlegm  remains  behind 

500.  Alcohol  may  be  mixed  with  water  in  every  pro« 


CONVERSION  OF  SUGAR  INTO  ALCOHOL.      509 

portion,  and  it  becomes  specifically  heavier  the  more 
water  it  contains  ;  therefore,  its  specific  gravity  is  a  very 
simple,  and  at  the  same  time  a  sure,  test  for  the  greater 
or  less  strength  of  alcohol.     This  is  most  conveniently 
ascertained   by  the   areometer  (alcoholometer).     Abso- 
lute alcohol  hAs  a  specific  gravity  of  0.792;  that  is,  a 
vessel  capable  of  containing  just  1,000  grains  of  \\ater 
is  entirely  filled  by  792  grains  of  absolute  alcohol ;  it  is 
accordingly  about  one  fifth  lighter  than  water.     In  this 
alcohol,  the  alcoholometer  sinks  to  the  topmost  point 
of  the   scale,  to  100°,  while  in  pure   water  it  sinks  to 
the  lowest  degree   only  of  the  scale,  which  is  marked 
0D  (§  16).     The  scales  most  in  use  are  those  of  Tralles 
and  Richter,  which  deviate  very  widely  from  each  oth- 
er, since    Tralles  made   the  mixtures   of   alcohol  and 
water  from  which  he  determined  the  degrees  by  meas- 
ure   or   volume,  while  Richter  made  them  by  weight. 
The  former,   for   instance,  called   that    alcohol   which 
consisted  of  one  measure  of  alcohol  and  one 
measure  of  water,  fifty  degrees ;  but  the  lat- 
ter gave  this  number  to  a  mixture  consisting 
of  one  pound  of   alcohol  and    one   pound  of 
waterj,     There  must,  of  course,  be  more  alco- 
hol in  the  latter  than   in  the  former   mixture, 
because    one    pound    of    alcohol    occupies    a 
greater  volume  than  one  pound  of  water ;   and 
thus  is  explained  why  one  and  the  same  alco- 
hol shows  more  degrees  on  Tralles's  alcohol- 
ometer,   and    consequently    appears    stronger 
than  by  Richter's. 
If  you  mix  50  measures  of  alcohol  and  50  measures 
of  water,  you  do  not  obtain   100  measures,  but  only 
about  97  ;  thus  a  condensation  takes  place,  as  in  the  mix- 
ing of  sulphuric  acid  with  water  (§  173).     This  explain* 
43* 


*>10  VEGETABLE     MATTER. 

the  heating  which  always  takes  place  when  water  and 
alcohol  are  mixed  together.  The  knowledge  of  this  fact 
is  of  economical  importance  for  those  merchants  who 
now  frequently  prepare  brandy  by  diluting  strong  spirit 
with  water,  since  this  liquid  is  commonly  sold  by 
measure. 

501.  Alcohol,  like  water,  is  a  solvent  for  many  sub- 
stances, and,  indeed,  it  not  only  dissolves  many  sub- 
stances which  are  also  soluble  in  water,  such  as  tannin, 
sugar,  &c.,  but  many  others,  which  are  insoluble  or  near- 
ly insoluble  in  water,  such  as  resins,  volatile  oils,  &c. 

Experiment.  —  Pour  into  a  flask,  containing  one  dram 
of  bruised  gall-nuts^  an  ounce  of  water,  and  into  anoth- 
er flask,  containing  the  same  quantity  of  gall-nuts,  an 
ounce  of  alcohol;  fasten  over  both  flasks  a  piece  of 
moistened  bladder,  in  which  some  holes  have  beep 
pierced  with  a  needle,  and  set  them  aside  for  some  days 
in  a  warm  place.  We  obtain  in  both  cases  dark-col- 
ored, very  astringent-tasting  liquids  (infusions  and  tinc- 
tures),  which  are  to  be  clarified  by  filtration.  They  both 
hold  in  solution  a  peculiar  principle  of  gall-nuts,  called 
tannin  or  tannic  acid.  The  watery  infusion  will  decom- 
pose after  a  time,  with  the  formation  of  vegetable 
mould;  but  not  so  the  spirituous  tincture,  because  al- 
crhol  has  the  power  of  preventing  the  commencement 
ot  putrefaction. 

Experiment.  —  Prepare  in  the  way  just  described 
an  infusion  from  one  dram  of  powdered  cinnamon 
and  water.  A  slightly  colored  liquid  is  obtained,  and 
this,  if  evaporated  on  a  warm  stove,  leaves  behind  an 
almost  tasteless  gum,  which  easily  dissolves  again  in 
water.  Now  pour  some  alcohol  upon  the  cinnamon 
that  remains,  arid  let  them  digest  for  several  days ;  we 
shall  obtain  a  dark-brown,  fiery,  spicy,  and  astringent 


CONVERSION    OF    ALCOHOL    INTO    ETHER. 

tasted  liquid  (tincture  of  cinnamon).  If  some  of  this 
tincture  is  evaporated  to  dryness,  a  brown,  glistening 
mass  (resin)  remains  behind,  which  may  be  redissolved 
in  alcohol,  but  not  in  water.  Besides  several  other  sub- 
stances, the  water  has  accordingly  dissolved  principally 
gum,  the  alcohdl  principally  resin  (and  volatile  oil)  from 
the  cinnamon. 

These  examples  are  sufficient  to  show  in  how  many 
ways  alcohol  may  be  employed  as  a  means  of  solution 
and  preservation.  The  principal  solutions  effected  by 
it  are, — 

a.)  The  tinctures  of  pharmacy,  alcoholic  extracts  oi 
medicinal  plants,  roots,  barks,  &c. 

b.)  The  lac  varnishes,  solutions  of  resin  in  alcohol. 

c.)  The  so-called  perfumed  waters,  eaude  Cologne,  so- 
lutions of  volatile  oils  in  alcohol,  &c. 

d.)  The  liqueurs  and  cordials,  solutions  of  volatile  oils 
(oil  of  cumin,  oil  of  peppermint,  &c.)  sweetened  with 
sugar,  or  of  bitter  and  aromatic  substances  (sweet-flag, 
cloves,  orange-peel,  &c.),  in  alcohol. 

Two  of  the  various  changes  which  alcohol  may  un- 
dergo are  specially  important,  namely,  its  conversion 
into  ether  and  vinegar. 


VII.     CONVERSION   OF    ALCOHOL    INTO 
ETHER. 

502.  Elayle,  or  Olefiant  Gas.  —  Experiment.  —  Mix 
very  gradually,  and  with  constant  stirring,  two  ounces 
of  common  sulphuric  acid  with  half  an  ounce  of  strong 
alcohol  (§  84) ;  the  heating  which  ensues  on  the  union 
of  these  two  fluids  is  still  greater  than  that  which  take* 


512 


VEGETABLE  MATTER. 


place  on  mixing  together  sulphuric  acid  and  water. 
When  the  mixture  is  cold,  pour  it  into  a  flask,  and  heat 
it  in  a  sand-bath  (see  Fig.  84),  at  first  cautiously,  that 
it  may  not  rise  over,  and  afterwards  somewhat  more 
strongly ;  a  kind  of  gas  is  evolved,  which  is  to  be  col- 
lected, as  has  been  described,  in  flasks  immersed  in  cold 
water.  Inflame  the  gas  contained  in  one  of  the  flasks, 
and  immediately  pour  in  water ;  it  burns  with  a  highly 
luminous  flame;  it  is  illuminating  gas  (C4H,),  which  is 
formed  from  the  alcohol.  The  alcohol 


Fig.  198. 


is  resolved  into  illuminating  gas  and 
water,  which  latter  combines  with  the 
sulphuric  acid  remaining  behind. 

Fig.  199. 


There  is  formed  from  alcohol,      illuminating  gas    and   2  water. 

There  are  likewise  formed  at  the  same  time  sulphur* 
ous  and  carbonic  acids,  the  former  of  which  may  easily 
be  recognized  by  the  smell ;  they  are  generated  by  the 
carbon  of  a  portion  of  the  alcohol  decomposing  a  por- 
tion of  sulphuric  acid,  and  abstracting  from  the  latter  its 
oxygen.  In  order  to  purify  the  illuminating  gas  from 
these  two  volatile  acids,  it  has  only  to  be  conducted 
through  milk  of  lime  before  it  is  collected. 

The  illuminating  gas  thus  obtained  has  received  the 
name  of  elayle^  or  olefiant  gas,  because  it  condenses  with 
the  chlorine,  forming  an  ethereal  liquid,  which,  like  oil, 
is  insoluble  in  water. 

503.  Sttlphuric  Ether.  —  Experiment. —  Mix  one  ounce 
of  strong  alcohol  with  one  ounce  of  common  sulphu- 
ric acid,  but  now  without  cooling  the  vessel  by  cold 


CONVERSION    OF    ALCOHOL     INTO    ETHER.  513 

water,  because  by  the  heating  of  the  mixture  the  desired 
chemical  change  is  promoted.  That  such  a  change  has 
really  taken  place  is  known  by  the  peculiar  smell,  differ- 
ent from  that  of  alcohol,  and  by  the  altered  (brownish) 
color  of  the  liquid.  The  change  which  a  portion  of  the 
alcohol  has  hereby  experienced  is  as  follows  :  — 

Fig.  200. 


There  is  formed  from  alcohol,  ether  (oxide  of  ethyle),       and 

While  in  the  former  experiment,  by  an  excess  of  sul- 
phuric acid,  two  atoms  of  oxygen  and  two  atoms  of  hy- 
drogen were  separated  from  the  alcohol,  in  the  latter 
case  the  alcohol  loses  only  half  as  much  of  these  two 
elements,  namely,  one  atom  of  each,  which  two  com- 
bine to  form  water.  From  the  alcohol  (C4H6O2) 
there  is  formed  a  new  body  (C4H5O)  which  has  re- 
ceived the  name  oxide  of  ethyle  (Ae  O),  because  it  is 
able,  like  a  base,  to  combine  with  acids.  In  the  pres- 
ent case  the  oxide  of  ethyle  meets  with  free  sulphuric 
acid,  with  which  it  combines,  forming  bisulphate  of 
oxide  of  'ethyle  ( Ae  O,  2  S  O3  +  4  H  O).  This  com- 
pound, which  is  contained  in  the  elixir  acidum  Halleri 
and  in  the  mistura  sulphurico-acida*  is  more  simply 
designated  by  the  name  of  sulphuric  ether. 

504.  Ether.  —  If  the  liquid  of  the  preceding  experi- 
ment, consisting  of  sulphuric  ether,  is  heated,  it  resolves 
itself  into  oxide  of  ethyle  (ether),  water,  and  sulphuric 
acid. 

Experiment.  —  Put  the  mixture  prepared  from  alcohol 
and  sulphuric  acid  into  a  flask  connected  with  a  glass 

*  Preparations  occurring  in  some  European  pharmacopoeias. 


514  VEGETABLE     MATTER. 

tube  and  a  receiver  (see  Fig.  106),  close  the  opening 
remaining  between  the  neck  of  the  receiver  and  the 
glass  tube  by  binding  round  it  a  piece  of  moistened 
bladder,  in  which  some  fine  holes  are  pierced,  and  heat 
the  flask  carefully  in  a  sand-bath  till  the  contents  of  it 
assume  a  bubbling  motion.  Maintain  the  boiling  of 
the  liquid  till  about  half,  or  at  most  three  quarters,  of 
an  ounce  of  the  liquid  is  distilled  over.  In  this  experi- 
ment the  liquor,  as  it  is  distilled,  must  be  subjected  to 
a  powerful  refrigeration,  because  it  is  extremely  vola- 
tile ;  it  is  therefore  advisable  to  perform  the  experiment 
in  winter,  and  to  surround  the  receiver  with  snow. 
Care  must  also  be  taken  not  to  bring  any  burning  sub- 
stance too  near  the  vapors  or  the  liquid  which  pass 
over,  as  they  are  both  exceedingly  inflammable.  The 
distilled,  colorless  liquid  possesses  a  penetrating,  pleas- 
ant smell ;  it  is  called  crude  ether. 

In  order  to  purify  it,  shake  it  up  in  a  small  vessel 
with  half  an  ounce  of  water,  and  one  dram  of  potassa 
lye ;  close  the  vial,  and  let  it  remain  standing  for  an 
hour  with  the  bottom  upwards.  Crude  ether  contains 
a  mixture  of  water,  alcohol,  and  frequently  also,  when 
the  distillation  is  continued  too  long,  some  sulphurous 
acid ;  these  substances  combine  with  the  water  and  the 
potassa  added,  and  form  with  them  the  heavier  liquid 
layer,  which  settles  at  the  bottom  of  the  vial.  The 
very  thin  and  mobile  liquid  floating  above  is  ether, 
which  separates,  because  it  comports  itself  towards  wa- 
ter in  the  same  manner  as  oil  does,  and  is  dissolved  by 
it  only  in  very  small  quantity.  If  you  now  loosen  the 
stopper  of  the  inverted  vial,  the  aqueous  liquid  will  run 
out,  while  the  ether  remains  behind.  If  the  latter  is  re- 
quired entirely  pure,  it  must  be  again  distilled  or  rectified 

The  most  profitable  way  of  preparing  ether  on  a 


CONVERSION    OF    ALCOHOL    INTO  ETHER.  515 

jarge  scale  is  the  following.  Nine  pounds  of  sulphuric 
acid  and  five  pounds  of  alcohol  are  mixed  together,  and 
heated  to  the  boiling  point.  While  the  mixture  is  still 
boiling,  just  so  much  alcohol  is  allowed  gradually  to 
drop  in,  as  there  is  ether  distilled  over.  One  single 
pound  of  sulphuric  acid  is  then  sufficient  gradually 
to  convert  into  ether  thirty  pounds  of  alcohol,  at  nine- 
ty per  cent.,  or  an  unlimited  quantity  of  absolute  al- 
cohol. 

505.  Explanation  of  the  Formation  of  Ether.  —  Alco- 
hol is  distinguished  from  ether  merely  by  this,  that  it 
contains  one  atom  of  hydrogen  and  one  atom  of  oxy 
gen,  consequently  one  atom  of  water,  more  than  the 
latter.  Accordingly,  the  production  of  ether  may  thus 
be  explained  in  the  simplest  manner:  sulphuric  acid, 
on  account  of  its  strong  affinity  for  water,  abstracts  from 
the  alcohol  one  atom  of  water,  and  thus  the  alcohol  is 
converted  into  ether.  But  the  process  is  somewhat  more 
complex,  because  there  ,is  an  intermediate  station  —  the 
bisulphate  of  oxide  of  ethyle  —  on  the  way  between  the 
At  i3oo to  1400  alcohol  and  the  ether.  This 

complex  compound,  having 
Ether.  the  character  of  a  salt,  acts 

very  differently  according  as 
it  is  heated  in  a  concentrat- 

Hyd  rated  sul- 
phuric acid.      e(j  or  jn  a  diluted  condition. 

When  diluted  with  six,  or, 

at  most,  with  eight  atoms  of  water,  this  compound 
boils  at  from  130°  to  140°  C.,  and  is  thereby  resolved 
into  ether,  water,  and  hydrated  sulphuric  acid  ;  the  two 
former  volatilize  without  combining  chemically  with 
each  other,  and  the  latter  remains  behind.  When 
the  bisulphate  of  the  oxide  of  ethyle  is  diluted  with 
from  nine  to  ten  atoms  of  water,  it  boils  even  at  a 


516 


VEGETABLE    MATTER. 


8- 9  HO — 


lower  temperature  than  130°  C.,  and  is  thereby  re- 
solved   into    alcohol    and 
hydrated     sulphuric    acid. 
Alcohol.  Here,  too,  ether  and  water 

are  first  separated,  but  both, 
when  in  a  nascent  state, 
combine  chemically  with 
each  other,  forming  alco- 
hol. This  is  the  reason  why,  in  the  last-mentioned 
method  of  preparing  ether,  the  sulphuric  acid  becomes 
ineffectual  after  it  has  transformed  thirty  times  its  own 
weight  of  alcohol  at  ninety  per  cent,  into  ether ;  it  has 
then  become  so  diluted  by  the  water  which  it  has  ab- 
stracted from  the  hydrated  alcohol,  that  nearly  nine 
atoms  of  water  have  combined  with  two  atoms  of  sul- 
phuric acid.  It  has  already  been  shown,  in  the  first 
part  of  this  work,  by  several  experiments,  how  other 
bodies  also,  at  different  temperatures,  evince  sometimes 
a  stronger,  sometimes  a  weaker  affinity  for  water,  or, 
indeed,  none  at  all  for  it. 

506.  Experiments  with  Ether. 

a.)  Pour  some  drops  of  ether  upon  the  hand ;  it  will 
evaporate  in  a  few  moments,  imparting  to  tl  e  hand  a 
perceptible  feeling  of  coldness  (§40).  Ether  is  so  very 
volatile  that  it  boils  when  in  summer  it  is  put  in  the 
sun  (at  35°  C.) ;  therefore  it  must  always  be  kept  in 
tightly  closed  bottles,  and  in  a  cool  place. 

b.)  Dip  one  piece  of  wood  into  ether,  another  into 
alcohol,  and  hold  both  to  the  flame  of  a  candle;  the 
ether  burns  with  far  greater  briskness,  and  also  with 
a  much  more  luminous  and  a  somewhat  fuliginous 
flame.  Its  stronger  illuminating  power  is  simply  ex- 
olained  by  its  containing  a  larger  amount  of  carbon* 


CONVERSION    OF    ALCOHOL    INTO    ETHER.  511"* 

The  process  in  burning  is  the  same  as  with  alcohol ; 
the  ether  being  also  converted  into  carbonic  acid  and 
water. 

c.)  If  you  pour  some  drops  of  ether  into  a  tumbler, 
and  after  some  minutes,  when  the  ether  is  converted  in- 
to vapor,  appjy  to  it  a  burning  taper,  a  sudden  ignition 
ensue*.,  accompanied  by  an  explosive  noise.  The  va- 
por of  ether  forms,  like  hydrogen  or  marsh  gas,  when 
mixed  with  atmospheric  air,  a  kind  of  explosive  gas, 
and  several  violent  explosions  have  been  occasioned  by 
carrying  lighted  candles  or  lamps  into  those  places 
where,  owing  to  the  breaking  of  a  bottle  filled  with 
ether,  its  vapor  has  become  diffused  in  the  air. 

d.)  Ether  may  be  mixed  with  alcohol  in  any  propor- 
tion whatever.  When  mixed  with  three  parts  of  alco- 
hol, it  is  much  used  as  a  stimulating  and  restorative 
medicine,  under  the  name  of  Hoffmann's  anodyne  liquor. 

e.)  Put  a  piece  of  tallow,  or  a  few  drops  of  olive  oil, 
into  a  test-tube  with  some  ether ;  both  will  entirely  dis- 
solve in  it.  But  they  are  not  soluble  in  alcohol  or  water. 
Therefore  ether  may  be  advantageously  employed  for 
dissolving  and  separating  such  substances  as  will  dis- 
solve in  it,  but  not  in  other  liquids.  Besides  fat,  many 
of  the  resins,  and  the  so-called  gum  elastic  (caoutchouc), 
are  soluble  in  ether. 

Ether  is  also  very  generally  called  sulphuric  ether  ;  but 
this  appellation  is  incorrect,  since  pure  ether  neither 
contains  sulphuric  acid,  nor  has  any  sulphur  in  its  com- 
position. 

507.   Combinations  of  Ether  with  Acids. 

It  has  already  been  stated,  that  ether,  though  it  does 
not  give  a  basic  reaction,  yet  comports  itself  as  a  base, 
that  is,  combines  with  acids.    These  combinations,  how- 
44 


518  VEGETABLE    MATTER. 

ever,  cannot  be  directly  produced  by  the  mixture  of 
ether  with  acids.  Ether  combines  with  acids  at  the 
moment  of  formation  only,  or  when  it  is  liberated  from 
some  other  combination ;  but  after  it  has  once  been  set 
free,  it  no  longer  shows  any  inclination  to  combine  with 
acids.  These  combinations  may  be  called  salts  of 
ether,  or  salts  of  oxide  of  ethyle,  just  as  the  terms  salts 
of  potassa  and  salts  of  potassium  are  used,  but  they  are 
generally  spoken  of  as  kinds  of  ether.  Most  of  them  are 
liquid,  and  have  a  volatile,  cooling  taste.  They  are  com- 
monly prepared  by  distilling  the  different  acids  with  alco- 
hol, and  often  in  the  presence  of  sulphuric  acid.  Those 
only  which  are  best  knojvn  will  be  here  alluded  to. 

Acetate  of  Oxide  of  Ethyle,  or  Acetic  Ether  (AeO, 
A),  is  a  very  volatile  liquid,  having  an  agreeable  odor, 
and  is  employed  in  medicine. 

Nitrite  of  Oxide  of  Ethyle,  or  Nitrous  Ether  (Ae  O, 
N  O3),  has  an  agreeable  odor,  like  that  of  fruit,  and  is 
contained,  diluted  with  alcohol,  in  the  spir.  nitr.  ceth. 
(sweet  spirits  of  nitre)  of  the  apothecaries,  which  is 
known  as  a  medicine. 

Chloride  of  Ethyle,  or  Muriatic  Ether  (Ae  Cl),  forms 
a  constituent  of  the  spirit  of  muriatic  ether. 

GEnanthate  of  Oxide  of  Ethyle,  or  (Enanthic  Ether 
( Ae  O,  Oe),  is  contained  in  wine,  and  is  the  cause  of 
the  so-called  bouquet  of  certain  sorts  of  wine. 

Butyrate  of  Oxide  of  Ethyle,  or  Butyric  Ether,  now 
occurs  in  commerce  under  the  name  of  rum-ether,  or 
essence  of  rum,  and  is  used  for  imparting  to  alcohol  an 
odor  similar  to  that  of  rum. 

508.   Organic  Radicals. 

Formerly  organic  substances  were  considered  as  im- 
mediate combinations  of  carbon,  hydrogen,  oxygen, 


CONVERSION    OF    ALCOHOL    INTO    ETHER.  M  9 

nitrogen,  &c. ;  accordingly  they  were  divided  into  ter- 
nary compounds  (having  three  elements),  quaternary 
(having  four  elements),  &c.  But  in  modern  times  the 
hypothesis  has  been  adopted,  that  a  simple  manner  of 
combination  may  exist  in  organic  substances  analo- 
gous to  that  of  the  inorganic  compounds;  namely,  that 
a  simple  group  of  atoms,  as  of  carbon  and  hydrogen, 
may  comport  itself  in  the  same  way  as  an  element  or  a 
radical ;  the  group  C2  N  (cyanogen),  for  instance,  com- 
ports itself  as  such.  This  supposition  has  already  been 
most  beautifully  confirmed  in  many  cases,  and  since 
alcohol  and  ether,  and  their  metamorphoses,  are  pecu- 
liarly adapted  for  illustrating  this  new  mode  of  consid- 
ering the  subject,  we  will  cite  them  as  examples.  In 
these  combinations  we  consider  a  group  of  four  atoms 
of  carbon  and  five  atoms  of  hydrogen  (C4H3)  as  the 
elementary  substance,  as  the  radical,  and  call  it  ethyle 
(Ae).  Accordingly,  we  now  regard  ether  (C4  H5  O)  as 
oxide  of  ethyle  (Ae  ^-  O) ;  alcohol  (C4  H6  OJ  as  hydrat- 
ed  oxide  of  ethyle  (AeO  +  HO);  sulphuric  ether  as 
bisulphate  of  oxide  of  ethyle  (Ae  O,2  S  O3  +  4  H  O) ; 
acetic  ether  as  acetate  of  oxide  of  ethyle  ( Ae  O,  A) ;  mu- 
riatic ether  as  chloride  of  ethyle  (Ae  Cl),  &c. 

It  will  be  readily  perceived  from  this  grouping,  that 
the  organic  compounds  show  a  surprising  resemblance 
to  the  inorganic,  and  may  be  very  well  compared  with 
them ;  the  ethyle  series,  for  instance,  with  the  potas- 
sium series,  in  the  following  manner:  — 

Potassium  corresponds  to  ethyle, 

Potassa  "          "       oxide  of  ethyle  (ether), 

Hydrate  of  potassa  "         "      hydrated  oxide  of  ethyle  (alcohol), 

Pisulphate  of  potassa       "         "      bisulphate  of  oxide  of  ethyle, 

Acetate  of  potassa  "         "      acetate  of  oxide  of  ethyle  (acetic  ether  \ 

Chloride  of  potassium      "         "      chloride  of  ethyle,  &c. 


520  VEGETABLE     MATTER. 

The  radicals  of  this  kind,  among  which  may  be  reck- 
oned, also,  cyanogen  and  ammonium,  are  termed  com- 
pound or  organic  radicals.  Ether  belongs  to  the  divis 
ion  of  radicals  forming  bases. 


VIII.     CONVERSION   OF   ALCOHOL   INTO 
VINEGAR. 

509.  Experiment.  —  Mix  in  a  glass  vessel  half  an 
ounce  of  brandy  with  three  ounces  vof  spring-water,  and 
put  in  the  liquid  a  slice  of  leavened  rye  bread,  or  black 
bread  (Sr.hwartzbrod)^  which  has  been  previously  soaked 
in  strong  vinegar,  or  instead  of  it  a  little  leaven  ;  cover 
the  vessel  with  a  piece  of  perforated  pasteboard,  and 
put  it  in  a  place  where  the  temperature  is  between 
30°  and  40°  C. ;  the  spirituous  liquor  will,  after  some 
weeks,  be  converted  into  vinegar.  This  conversion 
does  not  take  place  in  a  closed  vessel,  as  the  oxygen 
of  the  air  is  indispensable  to  the  process ;  a  great  quan- 
tity of  oxygen  is  consumed,  since  information  of  vine- 
gar consists  in  an  oxidation  of  the  alcohol  by  the  oxygen 
of  the  air.  Neither  is  any  vinegar  formed  if  you  do  not 
add  the  bread  or  the  leaven.  As  the  solution  of  sugar 
does  not  of  itself  pass  over  into  alcohol,  neither  does 
the  alcohol  of  itself  pass  over  into  vinegar.  But  as  an 
easily  resolvable  body  (ferment,  yeast,  &c.)  disposes 
sugar  to  enter  into  decomposition  simultaneously  with 
itself,  so  also  acid  bodies,  that  may  be  easily  decom- 
posed, such  as  black  bread,  leaven,  vinegar,  &o.,  are 
able  to  bring  the  alcohol  into  that  state  in  which  it  ab 
sorbs  oxygen.  The  mode  of  action  of  these  substances, 
which  are  called  vinegar  ferments,  resembles  that  of  the 


CONVERSION    OF    ALCOHOL    INTO    VINEGAR.  521 

nitric  oxide  in  the  sulphur-chambers ;  they  are,  like  the 
latter,  the  transferrers,  that  is,  they  attract  the  oxygen 
from  the  air,  and  give  it  up  again  to  the  diluted  alcohol. 

In  the  same  manner  with  pure  diluted  alcohol,  all 
other  alcoholic  liquids,  as  beer,  wine,  cider,  &c.,  may, 
by  receiving  oxygen,  be  converted  into  vinegar,  and  it 
is  well  known  that  vinegar  is  frequently  prepared  from 
them.  If,  as  is  ordinarily  the  case,  they  contain  gluten 
or  lees  in  solution,  then  these  substances  replace  thf 
vinegar  ferment,  and  the  acidification  ensues  sponta 
neously,  when  the  liquid  is  exposed  in  loosely  covered 
vessels  to  a  temperature  of  from  30°  to  40°  C.  This 
acidification  most  readily  occurs  immediately  after  a 
spirituous  fermentation,  which  has  taken  place  at  too 
high  a  temperature ;  for  this  reason,  in  the  hot  months 
of  summer,  the  brewers  and  brandy-distillers  find  diffi- 
culty in  keeping  their  fermenting  wort  and  mash  from 
turning  sour,  which  can  only  be  prevented  by  rapid 
refrigeration. 

Liquids,  also,  containing  starch  and  sugar,  may  pass 
over  into  vinegar,  but  only  after  these  have  been  pre- 
viously converted  by  fermentation  into  alcohol.  This 
explains  why  the  farmer  obtains  vinegar,  when,  having 
poured  water  upon  the  peels  and  refuse  of  fruit,  he  sets 
them  aside  near  the  stove ;  why  boiled  food,  preserved 
fruits,  &c.,  become  acid  after  a  time.  The  spirituous 
fermentation,  which  first  takes  place,  is  always  fol- 
lowed by  an  effervescence  or  fermentation  in  these 
cases,  because  the  carbonic  acid,  formed  from  the  sugar 
at  the  same  time  with  the  alcohol,  escapes.  From  this 
is  derived  the  term  vinegar  fermentation,  by  which,  in 
earlier  times,  the  process  of  the  formation  of  vinegai 
was  designated,  this  effervescence  being  regarded  as 
an  essential  phenomenon  in  the  generation  of  vinegar, 
44* 


522  VEGETABLE    MATTER. 

But  it  is  now  known  that  no  evolution  of  gas  takes 
place  during  the  conversion  of  alcohol  into  vinegar. 

510.  Experiment.  —  Fill   two  tumblers  loosely  with 
the  stalks  of  grapes,  and  fill  one  entirely  and  the  other 
only  half  full  with  wine,  beer,   or  a  mixture  consist- 
ing of  one  part  of  brandy,  one  part  of  beer,  and  six 
parts  of  water.     Put  both  vessels  in  a  warm  place,  and 
once  or  twice  every  day  pour  the  mixture  from  one 
vessel  into  the  other,  so  that  each  may  be  alternately 
full  and  only  half  full  of  the  liquid.     The  alcohol  con- 
tained in    the  brandy  will,  in  this  manner,  be  much 
more  rapidly  oxidized  into  vinegar,  because  the  liquid 
adhering  to  the  grape-stalks  is,  in  this  state  of  fine  di- 
vision, surrounded  by  air,  and  thus  has  a  far  better  op- 
portunity of  attracting  oxygen  from  the  latter.      The 
effervescence  taking  place  at  the  commencement  was 
owing  to   the   sugar  contained    in  the   beer   and   the 
grape-stalks,  and  which  was  first  converted  into  alco- 
hol and  carbonic  acid.     The  alcohol  thus  formed  was 
likewise  afterwards  changed  into  vinegar,  and  this  is 
the  reason  why  the  vinegar  thus  produced  is  more  acid, 
that  is,  richer  in  acetic  acid,  than  that  obtained  by  the 
former  experiment. 

511.  Quick  Method  of  making  Vinegar.  —  The  tran 
sition  of  alcohol  into  acetic  acid  takes  place  yet  more 
rapidly  by  subdividing  the  alcohol  still  further,  or  by 
exposing  a  still  greater  surface  of  the  liquid  to  the  air 
than  in  the  way  just  described.      This  is  effected  in 
the  following  manner. 

A  tub  four  or  five  yards  high  is  filled  with  shavings 
01  beech-wood,  and  is  furnished  with  a  perforated 
shelf,  which  is  placed  somewhat  below  the  upper 
opening.  Through  each  of  the  small  holes  a  straw  or 
a  piece  of  packthread  is  passed,  prevented  from  falling 


CONVERSION    OF    ALCOHOL    INTO    VINEGAR.          523 


through  by  a  knot  at  the  upper  end.      By  this  means 

an  extreme  division  of 
the  alcohol  is  effected,  as 
when  it  is  poured  in  at 
the  top,  it  only  trickles 
slowly  down  through  the 
holes  by  means  of  the 
straw  or  packthread,  and 
then  diffuses  itself  over  the 
shavings,  forming  a  very 
thin  liquid  layer,  which 
presents  to  the  air  a  sur- 
face many  thousand  times 
more  extensive  than  was 
produced  by  any  former 
method.  Several  large 
holes  are  bored  round  the  lower  part  of  the  tub,  and 
likewise  in  the  perforated  shelf;  glass  tubes  are  fitted 
into  the  holes  made  in  the  latter,  in  such  a  mannei 
that  the  liquid,  when  poured  into  the  top,  may  not  run 
off  through  them.  A  free  circulation  of  air  is  here- 
by produced,  the  cooler  air  enters  by  the  openings 
in  the  tub,  gives  up  its  oxygen  to  the  alcohol  diffused 
over  the  shavings,  and  in  consequence  of  this  oxida- 
tion, or  slow  combustion,  so  much  heat  is  evolved 
in  the  interior  of  the  tub,  that  the  temperature  rises  to 
40°  C.  The  air,  hereby  becoming  warmer,  and  con- 
sequently lighter,  passes  out  of  the  tub  through  the 
glass  tubes  in  the  shelf,  and  from  an  eighth  to  a  fourth 
poorer  in  oxygen  than  when  it  entered.  Strong  vinegai 
is  used  as  a  ferment  in  this  process,  the  tub  and  shav- 
ings having  previously  been  moistened  with  it,  and  a 
certain  quantity  being  also  added  to  the  mixture  oi 
which  is  to  be  converted  into  vinegar.  In 


524  VEGETABLE    MATTER. 

such  a  tub  (vinegar-generator),  heated  brandy,  beer, 
wine,  &c.  may  be  converted  into  vinegar  in  a  few 
hours,  by  being  passed  through  the  cask  three  or  four 
times ;  hence  this  is  called  the  quick  method  of  making 
vinegar. 

512.  Explanation  of  the  Process  of  forming  Vinegar. 
—  In  order  to  convert  alcohol  into  vinegar,  four  atoms 
of  oxygen  must  enter  into  combination  with  one  atom 
of  alcohol.  From  one  atom  of  alcohol  and  four  at- 
oms of  oxygen,  =  C4  H6  O.2  -f-  4  O,  are  formed  one  atom 
of  acetic  acid  and  three  atoms  of  water,  =  C4  H3  O3  -j- 
3  H  O.  The  alcohol  is  accordingly  oxidized  into  acetic 
acid  and  water. 

This  process  may  be  regarded  as  a  slow  and  imper- 
fect combustion,  and  we  shall  here  also  find  confirmed 
what  was  stated  of  the  combustion  of  wood  in  the  air 
(§  120),  and  of  the  combustion  of  sugar  by  nitric  acid 
(§  196) ;  namely,  that  the  easily  combustible  and  easily 
oxidized  hydrogen  combines  with  the  oxygen  before  the 
difficultly  combustible  carbon  does.  Here,  as  is  ob- 
vious, none  of  the  carbon  of  the  alcohol  is  consumed, 
but  one  half  of  its  hydrogen  is  consumed  or  oxidized  by 
the  oxygen  of  the  air,  one  atom  of  oxygen,  moreover, 
being  taken  from  the  air. 

Aldehyde.  —  We  have  thus  far  considered  only  the 
starting  point  (alcohol)  and  the  extreme  point  (acetic* 
acid)  of  the  process  of  the  formation  of  vinegar  ;  but 
half  way  between  these  two  there  is  a  peculiar  com- 
pound, which  may  be  regarded  as  half-converted  alco 
hoi,  or  half-made  vinegar.  Tt  is  formed  from  the  alco- 
hol when  two  atoms  of  oxygen  enter  into  combination 
with  it,  thereby  converting  two  atoms  of  its  hydrogen 
into  water.  The  name  aldehyde  (that  is,  al-  alcohol 
le-  from  which,  hyd-  hydrogen  is  taken)  has  been  given 
to  it. 


CONVERSION    OF    ALCOHOL    INTO    VINEGAR.          525 

From  alcohol,  =  C4  H6  O*  and  2  O, 
is  formed  aldehyde,  =  C4  H<  O2  and  2  H  O. 

This  compound  is  always  produced  in  the  first  period 
of  the  formation  of  vinegar,  and  occasions  the  peculiar 
suffocating  smell  often  perceived  in  vinegar-chambers. 
Aldehyde  very  gi^edily  attracts  two  more  atoms  of  ox- 
ygen from  the  air,  and  is  thereby  converted  into  hy- 
drated  acetic  acid  (H  O,  C4  H3  O3).  This  occurs  in  the 
second  period  of  the  formation  of  vinegar,  when  an  acid 
odor  prevails  in  the  vinegar-chambers. 

Aldehyde  may  be  very  easily  produced,  and  it  may  be 
readily  recognized  by  its  characteristic  odor,  when,  as 
was  directed  in  §  114,  a  glowing  platinum  wire  is  held  in 
alcohol  vapor,  or  yet  more  easily,  by  pressing  down  an 
alcohol  flame  by  a  wire  net.  In  both  cases  it  is  formed 
because  the  temperature  is  not  high  enough  to  effect  a 
complete  combustion  of  the  alcohol  vapor.  A  portion 
of  the  latter  then  takes  up  only  two  atoms  of  oxygen 
from  the  air,  and  there  is  produced  aldehyde  vapor, 
and,  together  with  this,  some  acetic  acid  and  other  gas- 
eous products. 

After  this  statement  of  the  process  of  the  formation 
of  vinegar,  it  will  no  longer  appear  strange  that  alde- 
hyde and  acetic  acid  are  formed  in  all  cases  when  alco- 
hol unites  with  bodies  which  are  rich  in  oxygen,  and 
which  readily  part  with  it,  as,  for  instance,  chromic 
acid,  nitric  acid,  black  oxide  of  manganese,  sulphuric 
acid,  &c. 

It  may  now  also  be  easily  explained  how  vinegar  is 
produced  from  wood  by  dry  distillation.  Wood  con- 
sists of  C6  H.;  O5 ;  acetic  acid  of  C4  H3  O3,  or,  if  multi- 
plied by  1|,  of  C6  H,i  O4£.  Consequently,  it  is  only 
necessary  to  abstract  a  little  hydrogen  and  oxygen  from 
ihe  wood,  in  order  to  transfer  it  into  acetic  acid. 


526  VEGETABLE    MATTER. 

513.  Acetyle.  —  Aldehyde  and  acetic  acid  may,  like 
ether  and  alcohol,  be  regarded  as  combinations  of  an 
organic  radical.     This  radical  is  called  acetyle  (Ac),  and 
it  is  assumed  to  be  composed  of  four  atoms  of  carbon 
and  three  atoms  of   hydrogen  (C4  H3).      Accordingly, 
aldehyde  (C4  H4  CX)  is  the  same  as  hydrated  oxide  of 
acetyle  ( Ac  +  O  +  H  O)  ;  acetic  acid  (C4  H3  O3)  is  the 
same  as  oxide  of  acetyle  (Ac  +  3O). 

Acetyle    belongs   to   the   class   of  radicals  forming1 
acids. 

514.  Properties  of  Vinegar.  —  Yinegar  is  an  acetic 
acid  diluted   with  much  water,  and  frequently  mixed 
also  with  foreign  substances,  which  it  obtains  from  the 
malt,  fruit,  wine,  &c.,  from  which  it  is  prepared.     The 
esteemed  yellow  or  brownish  color  is  often  imparted  to 

it  artificially  by  burnt  sugar,  or  extract  of 
chicory.  The  vinegar  which  occurs  in 
commerce  under  the  name  of  wood-spirit 
o  contains  in  every  hundred  measures  from 
10  eight  to  twelve  measures  of  acetic  acid, 
wine-vinegar  from  six  to  eight,  and  com- 
40  mon  table  vinegar  only  from  two  to  five ; 
50  the  rest  is  water.  In  order  to  ascertain 
the  strength  of  vinegar,  we  adopt  a  course 
similar  to  that  used  in  testing  carbonate 
of  potassa  (§  202)  ;  that  is,  we  examine 
how  much  of  some  base  (ammonia  is  the 
best)  a  fixed  quantity  of  it  is  able  to  neu- 
tralize. Glass  cylindrical  jars,  constructed  for  this  pur- 
pose, and  divided  into  degrees,  are  called  acetometers. 

If  vinegar  is  allowed  to  remain  for  some  time  exposed 
to  the  air,  it  begins  to  decompose  (to  putrefy),  and  so 
much  the  more  readily  the  weaker  it  is.  This  is  indi 
cated  sometimes  by  a  white  film  (mould),  sometimes  by 


CONVERSION    OF    ALCOHOL    INTO    VINEGAR.  527 

the  separation  of  gelatinous  matter  (vinegar  mother^ 
sometimes  by  the  generation  of  infusoria,  which  can 
often  be  distinguished  by  the  naked  eye  when  a  glass 
of  vinegar  is  held  towards  the  sun  (vinegar  eels).  Fur- 
ther decomposition  may  be  arrested  for  a  time  by  boil- 
ing the  vinegar. 

Vinegar  is  somewhat  less  volatile  than  water.  When 
it  is  distilled,  first  a  weaker,  and  finally  a  stronger,  col- 
orless vinegar  pasees  over  (distilled  vinegar),  and  the 
foreign  non-volatile  mixtures  remain  behind. 

When  vinegar  is  exposed  to  the  cold,  the  water  con- 
tained in  it  is  frozen  before  the  acetic  acid  is ;  hence, 
weak  vinegar  may  be  made  stronger  by  partial  freezing. 
Wine,  when  exposed  to  the  cold,  acts  in  the  same 
manner. 

To  impart  to  vinegar  a  more  pungent  or  more  acid 
taste,  such  substances  as  Spanish  pepper,  pellitory  root, 
and  indeed  sulphuric  acid,  are  sometimes  added  to  it. 
The  latter  adulteration  may  readily  be  detected  in  the 
following  manner. 

Experiment.  —  Fill  a  jar  half  full  of  water,  and 
place  upon  it  a  cup  containing  the  vinegar 
to  be  tested,  together  with  some  grape- 
sugar;  then  let  the  jar  remain  on  a  hot 
stove  till  the  vinegar  has  evaporated.  If 
the  residuum  is  of  a  black  color,  then  the 
vinegar  contains  sulphuric  acid.  When 
heated  over  hot  water,  the  vinegar  only  is  volatilized, 
while  the  sulphuric  acid,  if  any  is  present,  remains  be- 
hind, and  finally,  when  all  the  aqueous  particles  have 
vanished,  attains  such  a  strength,  that  it  decomposes 
the  sugar  and  chars  it. 


528  VEGETABLE    MATTER. 


CONVERSION  OF  SUGAR  INTO   LACTIC  AND  BUTYRIC 
ACIDS. 

515.  If  an  open  vessel,  containing  some  expressed 
juice  of  the  beet,  is  put  in  a  warm  place,  where  it  will 
be  heated  to  between  30°  and  40°  C.,  the  beet-juice  will 
enter  into  fermentation,  in  the  same  manner  as  in 
§  482  ;  but  when  the  fermentation  is  finished,  notwith- 
standing that  all  the  sugar  has  disappeared,  we  do  not 
find  any  alcohol  in  the  fermented  liquid,  but  a  peculiar 
acid  (lactic  acid),  and  H  mucilaginous  gummy  sub- 
stance. This  process  of  decomposition  has  been  called 
mucilaginous  fermentation;  it  very  remarkably  illus- 
trates the  extremely  different  kinds  of  decomposition 
of  one  and  the  same  organic  substance,  according  to 
the  temperature  at  which  the  decomposition  takes 
place.  At  a  temperature  of  from  10°  to  20°  C.,  the 
beet-juice  entered  into  spirituous  fermentation,  and  its 
sugar  was  resolved  into  carbonic  acid  and  alcohol ;  at  a 
higher  temperature  it  likewise  fermented,  but  in  this 
case  the  sugar  is  converted  into  carbonic  acid,  lactic 
acid,  gum,  and  some  other  products. 

The  sugar  contained  in  many  vegetable  substances 
likewise  undergoes  a  similar  change,  when  these  are 
mixed  with  salt,  and  kept  for  some  time  in  a  compressed 
state.  The  acid  taste  which  we  perceive  in  pickled 
cabbage,  beans,  gherkins,  &c.,  is  owing  principally  to 
lactic  acid,  which  is  formed  in  these  substances  in  a 
way  not  yet  thoroughly  investigated. 

But  beside  this  acid,  we  frequently  find  in  the  above- 
mentioned  pickles  another,  called  butyric  acid,  which 
imparts  to  them  their  peculiar  odor.  This  acid,  it 
seems,  may  also  be  produced  by  the  metamorphosis 
of  vegetable  mucus,  for  it  is  always  generated  when 


FERMENTATION    OF    BREAD.  529 

vegetable  mucilaginous  substances  —  for  instance,  al- 
thsea-root,  quince-cores,  linseed,  &c.  —  are  allowed  to 
remain  for  some  time  in  water. 


FORMATION  OF  ALCOHOL,  ACETIC  ACID,  AND  LACTIC 
ACID,  ON  THE  BAKING  OF  BREAD. 

516.  Meal.  —  The  seeds  of  the  various  kinds  of  grain 
which  we  use  in  the  preparation  of  meal  and  bread 
contain,  as  principal  constituents,  starch  and  gluten,  and 
also  a  little  sugar.  On  grinding  the  grain,  the  husks 
and  the  parts  contiguous  to  them,  which  are  rich  in 
oily  matter  (nitrogen  and  phosphate  of  lime),  separate, 
constituting  the  bran,  and  there  is  left  from  the  inner 
whiter  mass,  called  the  albuminous  substance,  the  meal. 
The  gluten  is  tougher,  and  more  difficult  to  grind,  than 
the  starch  ;  this  explains  why  the  finer  white  meal,  ob- 
tained by  repeated  sifting  (bolting),  is  richer  in  starch, 
while  the  coarser  and  darker  meal  is  richer  in  gluten 
The  nutritive  property  of  meal  is  to  be  ascribed  to  the 
azotized  gluten  ;  unbolted  meal,  and  bread  made  of  it,  are 
accordingly  more  nutritive  than  white  meal  and  white 
bread,  but  at  the  same  time  less  digestible  (soluble). 

Experiment.  —  Mix  some  flour  with  lukewarm  water 
to  a  thick  paste,  cover  it  with  a  board,  and  let  it  remain 
for  eight  or  ten  days  in  a  warm  place.  The  paste  is 
gradually  altered,  and  two  distinct  periods  may  be  ob- 
served during  the  change.  In  the  first  place,  on  the 
second  or  fourth  day  bubbles  of  air  are  evolved  from  it, 
having  an  acid,  unpleasant  smell,  and  the  dough  now 
possesses  the  capacity  of  converting  sugar  into  lactic 
acid,  as  may  be  readily  perceived  by  adding  a  little  of 
it  to  some  sugared  water,  and  letting  it  stand  in  a  warm 
alace.  After  six  or  eight  days  the  dough  acquires  a 
45 


530  VEGETABLE    MATTER 

pleasant  smell,  and  it  now  acts,  when  added  to  a  solu- 
tion of  sugar,  like  yeast ;  that  is,  it  effects  a  decompo- 
sition of  the  sugar  into  alcohol  and  carbonic  acid.  If 
the  dough  is  allowed  to  stand  yet  longer,  it  again  ac- 
quires an  acid  taste,  but  which  now  proceeds  from  the 
acetic  acid  into  which  the  alcohol  previously  generated 
gradually  passes  over  (leaven).  In  this  state  it  also 
excites  a  spirituous  fermentation  in  sugared  water ;  but 
this  spirituous  fermentation  immediately  passes  over 
into  the  acid,  into  vinegar  formation.  It  is  obvious, 
from  what  has  previously  been  stated,  that  the  different 
actions  of  the  flour,  when  in  a  state  of  decomposition, 
upon  the  sugar,  depend  upon  the  albuminous  matter, 
the  gluten,  contained  in  the  flour;  consequently,  we 
might  call  the  slightly  altered  gluten  a  lactic  acid  fer- 
ment, that  which  is  more  altered  an  alcohol  ferment, 
and  that  which  is  still  further  altered  a  vinegar  ferment. 

517.  Bread.  —  What  thus  takes  place  slowly  pro- 
ceeds rapidly  in  the  making  of  bread,  since  a  ferment 
is  purposely  added  to  the  flour,  which  has  been  stirred 
up  with  water. 

In  the  making  of  white  bread,  the  surface  yeast  of 
beer  is  used  as  a  ferment ;  this,  as  is  known,  is  the  most 
powerful  alcohol  ferment.  The  sugar  contained  in  the 
meal  is  thereby  resolved  into  alcohol  and  carbonic  acid, 
which  struggle  to  escape,  whereby  the  tough  mass  oi 
dough  is  disintegrated,  and  rendered  light  and  porous 
(rising  of  the  dough).  These  substances,  together  with , 
about  half  the  water  employed,  volatilize  by  the  rapid 
heating  in  an  oven,  having  a  temperature  of  from  160° 
to  180°  C.,  and  the  cellular  partitions  of  the  baked 
bread  attain  such  a  solidity,  that  they  retain  their 
form  and  place  even  after  cooling.  But  if  the  heat  of 
the  oven  is  not  sufficient,  or  the  dough  is  too  watery, 


*  FERMENTATION    OF    BREAD.  531 

then  the  partitions  harden  too  slowly,  and,  on  the  escape 
of  the  carbonic  acid,  collapse,  or  run  into  each  other 
(slack  baking).  This  happens  most  frequently  with 
dark  bread,  since,  in  consequence  of  its  amount  of 
gluten,  it  retains  the  water  more  obstinately,  and  ac- 
cordingly dries  and  hardens  more  slowly,  than  white 
bread,  in  which  the  starch  is  more  abundant. 

Leaven  is  commonly  used  as  a  ferment  in  the  prep 
aration  of  black  bread.  There  is  formed,  during  the 
process,  besides  alcohol  and  carbonic  acid,  a  little  acetic 
and  lactic  acids  (perhaps  also  some  butyric  acid),  which 
communicate  to  the  bread  an  acid  taste.  From  three 
pounds  of  flour  we  obtain  about  four  pounds  of  bread ; 
consequently,  a  quarter  of  the  bread  consists  of  fixed 
water.  The  light,  porous  bread  dissolves  easily  in  the 
stomach ;  we  say  that  it  is  easily  digestible,  and  that 
the  compact  heavy  bread  is  difficultly  digestible. 

518.  It  is  known  (§458)  jthat  starch  is  converted,  by 
roasting,  into  gum  (dextrine) ;  a  part  of  the  starch  un- 
dergoes, also,  this  change  in  the  oven,  particularly  on  * 
the   surface  of  the    baked   bread,    which   receives   the 
strongest  heat  from  the  roof  of  the  oven.     If  the  crust 
of  the  hot  bread  is  rubbed  over  with  water,  and'  the 
bread  is  then  replaced  for  a  few  minutes  in  the  oven, 
some  of  the  dextrine  is  dissolved,  and  forms,  after  the 
evaporation,  the   lustrous   coating   which   we    see   on 
loaves  of  bread,  and  rolls. 

519.  Carbonic  acid,  as  applied  to  the  rising  of  bread 
may  be  more  or  less  advantageously  generated  in  other 
ways  than  by  the  fermentation  of  sugar ;  indeed,  quite 
other  substances  may  be   used  for  the  purpose,  such 
as  those  which  become  aeriform  on  the  application  of 
heat. 

Experiment.  —  Mix  intimately  together  two  grains  of 


532  VEGETABLE    MATTER. 

finely  pulverized  bicarbonate  of  soda,  and  a  dram  and  a 
half  of  flour,  and  knead  the  mixture  into  a  dough  with 
one  dram  of  water,  to  which  four  drops  of  common 
muriatic  acid  have  previously  been  added.  Let  the 
dough  remain  for  some  time  in  a  warm  place,  and  then 
bake  it  on  the  hot  flue  of  a  stove,  or  in  a  spoon  over 
an  alcohol  lamp.  A  porous  mass  of  bread  is  obtained, 
because  the  carbonic  acid  of  the  soda  salt  is  expelled 
by  the  muriatic  acid,  and  raises  the  dough  while  it  is 
yet  soft.  The  common  salt  which  is  formed  remains 
behind  in  the  bread,  and  imparts  to  it  a  saline  taste. 
This  method  has  been  introduced  in  many  places  for 
making  bread,  cake,  &c.  on  a  large  scale. 

Experiment.  —  Rub  a  dram  and  a  half  of  flour  with 
some  grains  of  carbonate  of  ammonia,  and  then  knead 
it  with  a  dram  of  lukewarm  water  into  a  dough,  and 
treat  it  as  in  the  last  experiment.  In  this  case,  also,  the 
mass  will  become  light  and  porous  after  the  rising  and 
baking,  because  the  carbonate  of  ammonia  (salt  of 
hartshorn)  is  rendered  aeriform  by  the  heat,  and  during 
its  escape  the  particles  of  the  dough  are  forced  asunder. 
In  this  way  the  bakers  usually  prepare  their  light  and 
spongy  cakes,  as,  for  instance,  spice-cakes,  &c.  Alco- 
hol and  rum,  which  are  sometimes  kneaded  with  dough 
to  promote  the  rising,  act  in  a  similar  way. 


RETROSPECT  OF  THE  CHANGES  OF  SUGAR  AND 
ALCOHOL. 

1.   Sugar  is  converted,  — 

a.)  By  the  loss  of  oxygen  and  hydrogen,  into  water 
and  brown  substances  rich  in  carbon. 

b.)  By  the  addition  of  oxygen,  into  saccharic  acid, 
oxalic  acid,  and  water,  and  finally  into  carbonic  acicj 
and  water. 


RETROSPECT.  .  533 

e.)  By  contact  with  azotized  substances  at  a  low  tem- 
perature, into  (rich  in  hydrogen)  alcohol  and  (rich  in 
oxygen)  carbonic  acid  (spirituous  fermentation). 

d.)  By  contact  with  azotized  bodies  at  a  somewhat 
higher  temperature,  into  lactic  acid,  mannite,  and  many 
other  substances  (mucilaginous  fermentation). 

2.  By  the  changes  mentioned  under  c  and  e?,  the 
azotized  body  is  also  simultaneously  transformed  into 
new  combinations  (yeast,  ammoniacal  salts,  &c.). 

3.  The  conversion  of  the  sugar  into  alcohol  and  car- 
bonic acid,  and  that  of  the  azotized  body  into  yeast, 
take  place  at  a  low  temperature  slowly  (bottom  fermen- 
tation), at  a  higher  temperature  rapidly  (surface  fermen- 
tation). 

4.  Hitherto  alcohol  has  been  prepared  only  by  this 
method,  namely,  by  the  fermentation  of  sugar. 

5.  Starch  is  indeed  used  for  the  manufacture  of  alco- 
hol, but  it  must  always  be  previously  converted  into 
sugar. 

6.  Alcohol  is  converted,  — 

a.)  By  the  loss  of  all  its  oxygen  and  some  hydrogen, 
into  elayle  (olefiant  gas)  and  water. 

b.}  By  the  loss  of  some  oxygen  and  hydrogen,  into 
oxide  of  ethyle  (ether)  and  water ;  this  oxide  of  ethyle 
can  combine  as  a  base  with  acids  (compound  ethers). 

c.)  By  the  addition  of  oxygen,  into  aldehyde  and  wa- 
ter, and  by  still  more  oxygen,  into  acetic  and  other  acids. 
If  we  follow  the  process  of  oxidation,  as  it  proceeds,  we 
shah1  observe  the  following  order  of  changes :  — 

From  alcohol    and  oxygen  are  formed  aldehyde  and  water ; 
"    aldehyde  and  oxygen     "        "        acetic  acid ; 
"    acetic  acid  and  oxygen  "        "        formic  acid  and  water; 
"    formic  acid  and  oxygen  "        "        oxalic  acid  and  water ; 
"    oxalic  acid  and  oxygen  "        "        carbonic  acid. 

45* 


534  VEGETABLE    MATTER. 

7.  The  last  products  of  this  process  of  oxidation  are 
consequently  those  into  which  the  alcohol  passes  when 
it  burns  up,  namely,  carbonic  acid  and  water. 

8.  Sugar  belongs  to  the  organic  compounds  rich  in 
carbon,  alcohol  to  those  rich  in  hydrogen,  acetic  and  the 
other  acids  to  those  rich  in  oxygen. 


IX.    FATS   AND  FAT   OILS. 

520.  Experiment.  —  Break  open  an  almond,  and 
squeeze  the  white  meat  together  by  means  of  the  finger- 
nail ;  small  drops  of  fluid  will  be  expressed,  which  are 
slippery  to  the  touch,  and  render  blotting-paper  greasy 
and  transparent.  This  liquid  is  called  oil  of  almonds. 
If  the  almonds  are  first  pounded,  and  then  subjected  in 
a  cloth  to  strong  pressure,  we  shall  obtain  more  than 
one  fourth  of  their  weight  in  oil  of  almonds.  A  great 
many  plants  contain  a  similar  oily  juice,  especially  in 
their  seeds,  and  from  many  of  the  latter  oils  are  ob- 
tained by  pounding  and  expressing.  The  term  fat  oils 
has  been  given  to  this  kind  of  oils,  because  they  are 
unctuous  to  the  touch,  and  thick  flowing.  They  occur, 
but  less  abundantly,  in  almost  all  plants,  even  in  those 
where  we  should  not  expect  to  find  any  ;  for  instance, 
in  different  grains,  grasses,  &c. 

521.  Experiment.  —  Boil  some  fat  pork  cut  up  into 
small  pieces  for  some  time  in  a  little  water,  and 
while  the  soft  mass  is  yet  hot,  strain  it  through  a  linen 
cloth ;  a  fat  oil  will  float  on  the  surface,  but  it  is  fluid 
only  at  a  temperature  of  about  30°  C. ;  below  this  tem- 
perature it  congeals  into  a  solid,  yet  soft,  white  sub- 
stance. This  is  also  lubricating  to  the  touch,  and  pro. 


FATS    AND    FAT    OILS.  533 

daces  greasy  spots  on  paper.  Such  kinds  of  fat,  which, 
at  the  common  temperature,  have  a  soft  unctuous  con- 
sistency, are  called  lard,  or,  improperly,  fat;  and  the 
cellular  membrane  and  skin  remaining  in  the  cloth,  and 
saturated  with  fat,  are  called  scraps. 

522.  The  suet  of  mutton,  when  treated  in  the  same 
way,  yields  a  fat  which,  when  hot,  is  also  fluid,  like  oil, 
but  which,  when  cooled  only  to  about  36°  C.,  congeals, 
and  then  forms  tallow,  a  still  harder  substance  than 
lard.     By  boiling  and  roasting,  we  can  melt  out  fat 
from  all  animal  substances,  especially  from  those  of  the 
domestic  animals,  in  which  we  are  able  to  produce  a 
great  quantity  of  fat  by  keeping  them  confined,  and 
giving  them  a  plentiful  supply  of  food.     The  fats  ob- 
tained by  boiling  with  water  are  white,  as  thereby  they 
do  not  become  heated  above  100°  C. ;  while  those  ob- 
tained by  roasting  have  a  yellow  or  brown  color  (brown 
butter,  gravies  of  roast  meat,  &c.),  because  in  this  case 
a  portion  of  the  fat  becomes  burnt  by  being  subjected 
to  a  stronger  heat,  —  to  a  heat,  perhaps,  even  above 
300°  C.      In  a  strict  sense,  animal  fats  belong  to  the 
last   division   of   this   work,  but   they  agree    in   their 
properties  so  exactly  with  the  vegetable  fats,  that  the 
subject  will  be  rendered  more  intelligible  by  consider- 
ing them  together  under  the  same  head. 

The  fats  of  vegetables  are  mostly  Liquid  (fat  oils), 
those  of  the  carnivorous  Mammalia  and  of  birds  are 
soft  (lard),  and  those,  of  the  ruminating  Mammalia 
nard  (tallow). 

PROPERTIES  OF  FATS. 

523.  Experiment.  —  Rub  a  little  fat  upon  paper,  and 
place  it  upon  a  hot  stove  ;  the  grease-spot  will  not  dis- 


536  VEGETABLE    MATTER. 

appear,  however  long  the  paper  may  be  heated,  since, 
the  fats  are  not  volatile. 

Fats  not  only  spread  with  great  ease  on  paper,  but 
also  on  all  other  porous  substances ;  as,  for  instance,  on 
wood,  leather,  &c.  Since  the  fats  remain  soft  for  a  long 
time  in  the  interior  of  these  substances,  we  possess  in 
1hem  means  for  rendering  flexible .  substances  supple, 
and  of  maintaining  them  in  this  state.  For  this  reason, 
leather  harnesses  and  shoes  are  greased  from  time  to 
time ;  and  for  the  same  reason,  also,  the  leather-dresser 
impregnates  his  lamb-skins  with  fish  oil  in  the  fulling- 
mill,  to  give  them  greater  softness  and  pliability  when 
they  are  worked  up  into  gloves,  &c.  That  clay  and 
loam  have  a  great  power  of  absorbing  fat  is  obvious, 
as  these  substances  are  able  to  draw  out  again  the 
grease  that  has  been  soaked  into  wood  or  paper.  Thin 
substances  acquire  a  greater  transparency  when  their 
pores  are  filled  with  fat  instead  of  air ;  common  paper 
is  rendered  in  this  way  so  transparent,  that  it  may  be 
used  for  tracing  and  for  transparencies. 

524.  The  fats  float  upon  water  ;  they  have  accordingly 
a  less  specific  weight  than  water.  On  account  of  this 
property,  they  may  be  used  for  excluding  air  from  other 
bodies.  A  solution  of  green  vitriol  speedily  attracts 
oxygen  from  the  air,  and  deposits  brown  hydrated  ses- 
piioxide  of  iron  (§  285);  but  it  remains  unchanged  when 
±  is  covered  with  an  oily  film.  Freshly  expressed  lemon- 
•uice  ^oon  moulds  in  the  air ;  it  does  not  mould  under 
i  covering  of  oil.  Preserved  fruits  keep  much  longer 
Krhen  melted  butter  is  poured  over  them. 

Fats  are  insoluble  in  water ;  hence  they  may  be  used 
for  protecting  other  bodies  from  being  penetrated  by 
water.  By  greasing  with  tallow  or  fat,  we  render  our 
shoe-leather  impervious  to  moisture;  by  oiling,  we  pre- 


FATS    AND    FAT    OILS.  537 

vent  the  rusting  of  iron  in  the  damp  ail ;  and  by  a 
coating  of  linseed  oil,  or  linseed-oil  varnish,  we  guard 
against  the  penetration  of  dampness  into  wood,  sails, 
cordage,  and  their  consequent  rapid  moulding  and  rot- 
ting. Lumber  and  timber  saturated  with  oil  remain, 
as  has  been  sh6wn  by  late  experiments,  unchanged  in 
the  moist  earth,  while  common  wood  is  frequently  de- 
stroyed by  putrefaction,  in  the  course  even  of  a  few 
years. 

525.  Emulsion.  —  Experiment.  —  Shake  some  oil  and 
water  briskly  together  in  a  test-tube ;  the  oil  separates 
into  small  drops,  and  renders  the  water  milky;  but  on 
quietly  standing,  it  soon  rises  again  to  the  surface.  It 
is  kept  in  suspension  in  the  water  much  longer  when 
some  mucilaginous  substances,  such  as  gum  or  albu* 
men,  are  contained  in  the  water ;  as  may  be  seen  by  trit 
urating  some  oil  with  albumen,  yolk  of  eggs,  or  a  thick 
solution  of  gum  Arabic,  and  afterwards  gradually  add- 
ing water.  The  milky  fluid  thus  obtained  is  called 
an  emulsion  (oleaginous  emulsion),  and  the  oil  in  it  will 
not  separate  from  the  water  till  after  some  days. 

Experiment.  —  A  second  mode  of  preparing  emul 
sions  consists  in  bruising  seed  rich  in  oils,  such  as  al- 
monds, or  rape-seed,  in  a  mortar,  and  gradually  adding 
water.  In  all  these  seeds  mucilaginous  and  albumi- 
nous substances  are  present,  which  are  dissolved  by 
water,  and  effect  a  fine  division  of  the  oil. 

We  have  a  natural  emulsion  in  the  milk  of  milch  ani- 
mals. Cow's  milk  is  turbid,  because  the  butter  floats 
about  in  it  in  small  globules,  invisible  to  the  naked  eye ; 
these  globules  of  fat  are  kept  suspended  in  the  watei 
because  a  body  similar  to  albumen  —  the  caseine  —  is 
dissolved  in  the  milk.  On  longer  standing,  the  caseine 
becomes  insoluble  (it  coagulates),  and  the  lighter  buttei 
collects,  as  cream,  upon  the  surface  of  the 


538  VEGETABLE    MATTER. 

526.  Drying  Oifs  and  Unctuous  Oils.  —  Experiment.  — 
Rub  upon  a  copper  coin  a  drop  of  linseed  oil,  upon 
another  a  drop  of  olive  oil,  and  let  them  both  remain 
for  several  days  in  a  warm  place ;  the  linseed  oil  will 
dry  up  into  a  resinous  solid  mass,  while  the  olive  oil 
will  remain  greasy.     All  oils  absorb  oxygen  from  the 
air,  and  become  thereby  thicker,  and   also  acquire  a 
disagreeable  smell  and  taste  (rancid) ;  but  there  is  an 
essential  difference  between  them,  as  many  oils  become 
perfectly  hard  and  dry,  while  others,  on  the  contrary, 
remain  soft  and  sticky.     Accordingly,  oils  are  divided 
into  two  classes,  into  drying  and  unctuous  oils.     The 
former  may  also  be  called  varnish  oils,  as  they  are  par- 
ticularly adapted  for  varnishing.     The  latter  are  called 
unctuous  oils,  because,  when  it  is  desired  to  prevent, 
by  means  of  grease,  the  friction  and  heating  of  solid 
bodies,  these  oils  remain  soft  and  unctuous  much  longer 
than  the  drying  oils. 

527.  By  the  absorption  and  condensation  of  oxygen 
taking  place  on  the  drying  of  oils,  heat  must  be  liberat- 
ed, as  in  every  condensation  of  an  aeriform  body  to  a 
liquid  condition.     Under  some  circumstances,  as  when 
freshly  oiled  or  varnished   substances,  such   as   wool, 
linen,  &c.,  are  closely  heaped  together  in  large  masses, 
this  heat  rises  to  such  a  degree,  that  spontaneous  com- 
bustion  occurs ;   therefore  it  is  not  prudent  to  lay  such 
articles  too  closely  upon  each  other,  before  they  have 
become  thoroughly  dry. 

CHANGES   OF  FAT  BY  HEAT. 

528.  Experiment.  —  Heat  some  linseed  oil  over  an 
alcohol  flame,  and  test  the  temperature  of.it  occasion- 
ally by  a  thermometer.     At  first  the  heat  rapidly  rises  to 


FATS    AND    FAT    OILS. 


539 


Ffc.  204. 


100°  C.,  and  remains  for  some 
time  at  that  temperature,  dur- 
ing which  time  the  oil  boils 
moderately ;  this  behaviour  is 
occasioned  by  all  crude  oil 
containing  watery  particles, 
which  evaporate  at  100°  C. 
As  soon  as  these  have  vol- 
atilized, the  temperature  is 
suddenly  elevated  even  above 
300°  C.,  when  the  oil  begins  to  boil  for  the  second 
time,  but  emitting  now  a  white  smoke  having  a  very 
disagreeable  odor.  This  vapor  consists  of  decom- 
posed oil,  principally  of  illuminating  gas,  and  burns, 
when  kindled,  with  a  brisk  flame ;  fats  are  accordingly 
combustible,  but  only  at  a  temperature  sufficiently  high 
to  effect  their  chemical  decomposition. 

Illuminating  gas  is  frequently  prepared  on  a  large 
scale  from  oils,  by  causing  them  to  drop  upon  a  red-hot 
iron  vessel,  from  which  the  gas  generated  (oil  gas)  is 
conducted  by  a  pipe  into  a  receiver  (gasometer). 

529.  Every  lamp,  every  candle,  is  an  illuminating- 
gas  apparatus  on  a  small  scale.  But  in 
this  case  the  combustion  takes  place  only 
with  the  aid  of  an  easily  combustible  body, 
the  wick.  When  a  fresh  candle  is  lighted, 
the  cotton  of  the  wick  first  inflames,  and 
the  heat  thus  produced  is  sufficient  to 
melt  the  tallow  in  contact  with  the  wick. 
The  melted  tallow  now  ascends  by  capil- 
lary attraction  (§  106),  through  channels 
formed  by  the  fibres  of  the  cotton  lying  be- 
side each  other,  and  in  these  channels  it 
becomes  heated  by  the  flame  to  a  temperature  of  above 


Fig.  205. 


540  VEGETABLE    MATTER. 

300°  C.,  and  consequently  is  decomposed  into  illumi- 
nating gas.  Whale  oil,  rapeseed  oil,  oil  of  colza, 
olive  oil,  tallow,  and  wax  are  most  frequently  used  as 
ilium  mating  materials. 

530.  Experiment.  —  Let    some    drops   of  water    fall 
from   a   shaving,  that  has  been  dipped-  in  water,  into 
some  oil  burning  in  a  spoon ;  the  oil  spatters  about, 
because  the  heavier  water  sinks  in  it  and  is  suddenly 
converted  into  vapor,  which  ejects  the  oil.     Burning  fat, 
such  as  varnish,  lard,  &c.,  should  therefore  never  be 
quenched  with  water ;  but  the  quenching  may  be  done 
easily  and  without  danger,  if  the  vessel  is  covered  with 
a  board  or  a    piece  of  sheet-iron,  thus  excluding  the 
air,  which  is  requisite  for  continued  combustion. 

531.  As  in  wood  (§  120),  so  also  in  fats,  the  hydro- 
gen burns  more  briskly  than  the   carbon,  and  this  is 
the  reason  why  the  partly  burnt  oil  remaining  after  the 
extinction  is  richer  in  carbon,  and  has  a  darker  color. 
An  empyreumatic  oil  of  this  kind  is  kept  by  the  Euro- 
pean apothecaries,  under  the  name  of  oil  of  bricks,  or 
philosophic  oil.      On  yet   further  heating,   the   linseed 
oil  becomes  continually  blacker,  and  at  the  same  time 
thicker,  so  that  it  finally  acquires  a  viscid  consistency, 
(factitious  birdlime),  and  when  mixed  with  soot  forms 
the  basis  of  the  important  printing-ink. 

COMPOSITION    OF   FATS. 

532.  The  similarity  in  the  combustion  of  fats  and 
food  indicates  that  they  have  a  similar  constitution. 

mdeed,  both  bodies  possess  the  same  constituents,  name- 
iy,  carbon,  hydrogen,  and  oxygen ;  the  difference  depends 
only  upon  the  quantity;  the  fats  contain,  namely,  more 
hydrogen  and  less  oxygen  than  wood.  They  accord- 


FATS    AND    PAT    OILS.  541 

ingly  belong  to  one  and  the  same  category  with  alcohol 
and  ether,  —  to  that  of  the  organic  bodies  which  are 
rich  in  water. 

533.  Stearine  and  Oleine.  —  We  cannot,  ho\ve\  er, 
regard  fats,  Like  woody  fibre  or  alcohol,  as  homogene- 
ous bodies,  brit  as  mixtures  of  several  more  simple  kinds 
of  fat,  into  which  the  fats,  without  being  chemically 
decomposed,  may  be  separated. 

Experiment.  —  If,  during  the  winter,  you  place  a  ves- 
sel containing  lamp  oil  in  the  cold,  part  of  it  will  con- 
geal into  a  solid  mass,  like  tallow,  while  the  other 
part  remains  fluid  ;  the  oil  is  accordingly  separated  by 
the  cold  into  two  fats,  one  solid  and  one  fluid.  The 
solid  fat  has  received  the  name  of  stearine,  the  fluid 
that  of  oleine.  By  repeated  cooling,  the  greater 
part  of  the  stearine  may  be  separated  from  the  oil. 
The  stearine  obtained  is  pressed  between  blotting- 
paper  as  long  as  the  paper  absorbs  any  liquid  oil 
(oleine). 

Experiment. — Twist  a  wire  round  a  wide-mouthed 
vial,  in  such  a  manner  as  to  form  two 
handles,  by  means  of  which  the  vial 
may  be  suspended  in  a  jar,  which  is 
then  half  filled  with  water,  and  heated 
upon  a  tripod.      Put  into  the  vial  one 
dram  of  tallow  and  enough  strong  al- 
cohol —  absolute  alcohol  is  the  best  — 
to  fill  it  three  quarters  full.     When  the 
contents  of  the  vial  boil,  remove  the  lamp,  and  leave 
the  vial  in  the  water-bath,  till  the  melted  tallow  has 
again  settled  at  the  bottom,  and  then  pour  the  hot  su- 
pernatant  alcohol   into    a  beaker-glass.       Repeat   the 
boiling  three  or  four  times,  with  fresh  alcohol.     Let  the 
alcohol    stand   for  some   hours  in  cold  water,  covered 
46 


542  VEGETABLE    MATTER. 

over;  afterwards  filter  the  liquid  from  the  granular 
powder  that  has  separated,  wash  the  powder  several 
times  with  cold  alcohol,  and  dry  it  in  an  airy  place. 
This  mass,  which,  when  dry,  is  laminated  and  slightly 
lustrous,  is  the  stearine  of  mutton-tallow;  the  oleine 
must  be  sought  for  in  the  filtered  alcohol.  It  remains 
behind,  in  the  form  of  a  somewhat  thick  oil,  when  the 
alcohol  is  allowed  to  evaporate  in  a  cup  on  a  warm 
stove. 

As  is  obvious  from  these  experiments,  stearine  and 
oleine  form  the  approximate  constituents  of  fat,  and  this 
is  the  reason  why  some  fats  are  hard,  some  soft,  and 
others  liquid;  the  solid  stearine  predominates  in  the 
former,  the  fluid  oleine  in  the  latter.  Pure  stearine  be- 
gins to  melt  at  60°  C.,  pure  oleine  begins  to  solidify 
only  at  a  very  low  temperature.  One  pound  of  mut- 
ton contains  about  three  quarters  of  a  pound  of  stea- 
rine ;  one  pound  of  olive  oil  barely  a  quarter  of  a 
pound. 

The  following  are  among  the  most  important  fats: — 

A.     VEGETABLE  FATS. 

a.     Drying  Oils  ( Varnish  Oils). 

534.  Linseed  Oil.  —  The  well-known  linseed  yields, 
on  being  subjected  to  pressure,  a  yellow  oil,  equal  to 
one  fifth  of  its  own  weight,  which  is  gradually  bleached 
by  long  exposure  to  the  sunlight.  It  is  most  frequently 
used  in  oil  varnishes. 

Experiment.  —  Add  to  an  ounce  of  linseed  oil  a  quar- 
ter of  a  dram  of  litharge,  and  half  a  dram  of  acetate  of 
lead  ;  put  the  mixture  in  a  warm  place,  and  frequently 
shake  it.  The  liquid,  clarified  by  settling,  now  dries 
much  quicker  than  it  would  have  done  before  ;  it  is  the 


FATS    AND    FAT    OILS. 


545 


common  linseed-oil  varnish,  which,  mixed  with  colors, 
is  generally  used  for  imparting  a  gloss  to  wood,  metal, 
&c.  The  so-called  oil-cloth  is  cotton  cloth  smeared 
with  colored  varnish ;  oil-silk  is  varnished  silk.  This 
varnish  is  c»mmonly  prepared,  on  a  large  scale,  by  heat- 
ing one  hundred  pounds  of  linseed  oil  with  one  pound 
of  litharge,  and  maintaining  the  mixture  for  an  hour  at 
a  temperature  of  100°  C.  A  stronger  heat  renders  the 
varnish  darker  and  thicker,  and,  besides,  might  easily 
cause  it  to  boil  over  and  take  fire.  The  slimy,  dingy 
white  sediment  which  remains  after  both  processes  is 
a  combination  of  mucilaginous  substances  with  oxide 
of  lead.  All  oils  contain,  in  the  unpurified  state;  mu- 
cilaginous (gummy  and  albuminous)  substances,  which 
retard  the  drying ;  these  are  rendered  insoluble  by  oxide 
of  lead.  Varnish  is,  accordingly,  Linseed  oil  free  from 
mucilage. 

By  kneading  together  linseed-oil  varnish  and  chalk, 
we  obtain  a  plastic  dough,  common  putty. 

Hemp  oil,  from  hemp-seed,  of  a  yellowish-green 
color,  is  also  used  in  the  preparation  of  varnish,  and 
likewise  for  burning,  and  for  the  manufacture  of  green 
soap. 

Poppy  oil,  from  poppy-seeds,  serves  as  a  table  oil, 
and  for  the  preparation  of  a  very  clear  varnish. 

Castor  oil,  from  the  seeds  of  the  castor-oil  plant,  is  a 
purgative  medicine. 

Oil  is  also  obtained  from  pumpkin-seeds,  walnuts, 
sunflower-seeds,  &c. 

b.     Unctuous  Oils  (remaining'  viscous). 

535.  Oil  for  burning  is  expressed  from  rapeseed. 
In  order  that  it  may  burn  without  depositing  soot  on 
the  wick,  it  must  be  refined,  that  is,  purified  from 


t)44  VEGETABLE    MATTER. 

its  slimy  parts.     This  is  done,  not  by  oxide  of  lead,  but 
by  sulphuric  acid. 

Experiment.  —  Mix  one  ounce  of  crude  rape  oil  with 
eight  drops  of  common  sulphuric  acid,  arid  shake  it 
frequently ;  in  half  an  hour  add  half  an  ounce  of  water, 
again  shake  the  mixture  briskly,  and  set  it  aside  for 
some  days,  when  the  oil  floating  on  the  surface  will  be 
freed  from  slime  (refined).  The  slimy  parts,  charred  by 
the  sulphuric  acid,  and  rendered  insoluble,  are  found 
settled  in  the  water  at  the  bottom  of  the  vessel.  The 
sulphuric  acid  yet  adhering  to  the  oil  is  removed  by  re- 
peated washing  with  water.  Sulphuric  acid  chars,  as 
is  known,  all  organic  substances  (§  173),  some  (for 
instance  mucilage)  easily,  others  (for  instance  oil)  with 
difficulty ;  if  just  enough  sulphuric  acid,  therefore,  is 
added  to  the  oil  to  char  the  mucilage,  then  the  muci- 
lage only  is  destroyed,  and  the  oil  remains  un decom- 
posed. A  larger  quantity  of  sulphuric  acid  would  also 
attack  the  oil. 

Olive  oil  is  pressed  out  from  the  pulp  of  olives,  the 
fruit  of  the  olive-tree.  The  finest  cold-pressed  Prov- 
ence oil  is  of  a  bright  yellow  color,  the  hot-pressed 
common  olive  oil  is  greenish ;  these  two  sorts  are,  as  is 
well  known,  universally  used  as  a  table  condiment, 
and  for  greasing  machinery.  There  is  a  thicker,  darker 
kind,  of  an  inferior  quality,  which  is  used  in  France 
and  Italy  for  the  manufacture  of  the  so-called  Naples 
or  Marseilles  soap. 

Oil  of  almonds  is  obtained  by  subjecting  sweet 
almonds  to  pressure.  Bitter  almonds  also  yield  by 
cold  pressure  a  good  oil  of  almonds,  while  by  hot  pres- 
sure an  oil  is  obtained  containing  prussic  acid. 

Oils  are  obtained  also  from  hazle-nutn,  beech-nut^ 
plum  and  cherry  stones,  apple-seeds,  &c. 


FATS    AND    FAT    OILS. 

Cocoa-nut  oil,  from  the  meat  of  the  cocoa-nut,  is,  at 
average  temperatures,  as  soft  as  hog's  lard ;  it  has  a 
white  color  and  a  somewhat  disagreeable  smell. 

Palm  oil,  a  yellow  fat,  similar  to  butter,  likewise  pro- 
ceeds from  the  fruit  of  a  species  of  palm-tree.  Its 
yellow  cctarin£  matter  is  removed  when  heated  to 
130°  C.  (bleaching  by  heat). 

Cocoa-nut  oil  and  palm  oil  are  now  manufactured 
into  soap  in  very  large  quantities. 

The  following  kinds  of  fat  are  employed  in  phar- 
macy :  — 

Butter  of  cacao,  the  tallow-like  white  or  yellowish 
fat  of  the  cacao-nut,  the  cause  of  the  fat  particles 
which  rise  on  boiled  chocolate. 

Oil  of  nutmegs,  the-  yellow,  agreeably-smelling  fat  of 
the  nutmeg,  having  the  consistency  of  butter. 

Oil  of  bays,  the  beautifully  green,  suet-like  fat  of  the 
berries  of  the  laurel-tree. 


B.  ANIMAL  FATS. 

536.  Our  common  domestic  animals,  cows,  goats, 
and  sheep,  supply  us  with  several  kinds  of  fat;  —  a 
harder,  white  land  (tallow  or  suet),  which  lies  in  and 
over  the  flesh ;  a  softer  kind,  generally  of  a  yellow  color, 
which  separates  from  their  milk  (butter) ;  and,  besides 
these,  there  are  the  fats  of  the  marrow  and  the  feet. 

Stag-grease  is  white  and  hard,  like  mutton-tallow. 

Hog's  lard,  goose-grease,  &c.,  are  well  enough  known. 
In  earlier  times,  when  it  was  believed  that  each  single 
animal  fat  concealed  within  itself  peculiar  properties, 
numerous  kinds  of  such  fats  were  kept  on  hand  in  the 
apothecaries'  shops ;  but  now,  plain  hog's  lard  supplies 
the  place  of  all  the  others. 
46* 


546  VEGETABLE    MATTER. 

537.  Fish  oil  is  tried   out  from  the  fat  of  whales, 
dolphins,    seals,    and    diilerent   fishes.     The   fat,  when 
melted  out    at    a  moderate    heat,   has   a    yellow    color, 
and  a  slight  odor,  which   is   not   disagreeable;   but  that 
whieh  is  obtained   by  strong  heat,  or  from  iishes  that 
have  beeome  putrid,  is  of  a  dark-brown  color,  and  has 
a    very    disagreeable    odor.      Fish    oil  is   preferred   for 
greasing  leather;  it  is  likewise  used  in  medicine  and 
in  the  preparation  of  the  black  oil-soap. 

538.  Spermaceti  is  white,  sparkling,  and  so  hard  that 
it  may  be  rubbed  into  a  powder,  and  is  found  inclosed 
in  special  cavities  in  the  head  of  the  sperm-whale. 

539.  Wax  (eera)   occurs   in  small  quantities  in  all 
plants,  especially  in  the  shining  coating  of  the  leaves, 
stalks,  and   fruits;    for   instance,    in  the   skins   of  ap- 
ples, and  particularly  in  the  pollen  of  flowers.     Some 
plants  of  Japan  and  South  America  contain  so  much 
wax  that  it  may  be  separated  by  boiling  with  water 
and  by  pressure,  and  it  is  then  introduced  into  com- 
merce under  the  name  of  vegetable  or  Japan  wax.     But 
the  purveyors  of  our  common  wax  are  the  bees,  who 
gather  it  from  the  flowers,  and  use  it  in  the  building  of 
their  cells.      These  insects   may,  perhaps,  make  their 
wax  in  part  also  from  the  sweet  juices  of  the  plants  on 
which  they  feed,  for  accurate  experiments  have  proved 
that  bees    have   the    capacity   of  exuding   from    then- 
abdominal  sacs  the  sugar  upon  which  they  feed,  con- 
verted into  wax.     The  yellow  wax  is  bleached  by  cut- 
ting  it  into  shavings,  exposing  them  to  the  sun,  and 
frequently  watering  them.     The  yellow  wax  melts  at 
62°  C.,  the  white  wax  at  70°  C.    Wax  is  not  only  used 
for  imparting  stillness  to  thread,  and  in  the  manufacture 
of  candles,  but  when  dissolved  in  potash  lye  it  forms 
the  so-called  wax -soap,  employed  for  giving  a  gloss  to 


FATS    AND    FAT    OILS.  54V 

variegated  paper  and  for  polishing  floors,  and  when 
mixed  with  oils  is  made  into  plasters  and  ointments 
(cerates).  Paper  immersed  in  hot  wax  forms  a  good 
material  for  covering  vessels,  to  protect  them  from 
moisture,  Turpentine  is  added  to  wax,  in  order  to  ren- 
der it  more  pliant  *and  tougher,  as  we  find  it  in  wax 
candles,  and  in  the  wax  used  for  grafting  trees. 

FATS  AND  ALKALIES  (SOAPS). 

540.  Hard  Soap.  —  Experiment.  —  Make  first  a  strong 
lye  with  one  dram  of  caustic   soda 

Fig-  207.  J 

of  commerce  and  one  ounce  of  wa- 
ter, and  next,  a  weak  lye,  with  one 
dram  of  caustic  soda  and  two  oun- 
ces of  water.  Boil  the  latter  gently 
with  an  ounce  and  a  half  of  beef- 
tallow,  for  half  an  hour,  in  a  vessel 
only  half  filled  with  the  mixture,  "and 
then  add  the  strong  lye  gradually  while  the  boiling 
continues.  The  fat  and  lye  unite  by  degrees  to  a  uni- 
form mass,  of  a  gluey  consistency,  which  after  a  time 
becomes  thick  and  frothy.  If  a  drop  of  this,  when 
pressed  between  the  fingers,  presents  firm  white  flakes, 
then  add  half  an  ounce  of  common  salt,  boil  for  some 
minutes,  and  let  the  whole  mass  quietly  cool.  We 
obtain  a  firm  mass  (soap)  and  a  watery  liquid,  in 
whieh  the  common  salt  and  some  free  soda  remain  dis- 
solved (under  lye).  If  the  soap,  when  boiled 'with 
water,  forms  a  turbid  solution,  it  contains  still  some 
unsaponified  tallow,  in  which  case  add  to  it  some  weak 
lye,  and  continue  boiling  until  the  sample  gives  a  clear 
solution  in  water;  add  again  some  table  salt,  and  let  it 
cool  The  soap  prepared  in  this  manner  has  the  same 


548  VEGETABLE    MATTER. 

composition  as  common  house-soap.  More  recently 
palm  oil  or  cocoa-nut  oil  has  been  used  partly  or  en 
tirely  to  supply  the  place  of  tallow,  the  palm  oil  be- 
cause it  is  cheaper  than  tallow,  and  the  cocoa-nut  oil 
because  it  communicates  to  the  soap  the  property  of 
forming  a  strong  lather. 

Experiment.  —  Repeat  the  former  experiment,  using 
o.Jve  oil  instead  of  tallow ;  hard  soap  is  likewise  ob- 
tained (olive  oil  or  Marseilles  soap). 

541.  Soft  Soap.  —  Experiment.  —  Prepare  again  some 
oil-soap,  as  above  described,  but  instead  of  soda  use 
potassa  lye,  which  is  prepared  from  caustic  potassa  and 
water,  and  omit  the  addition  of  common  salt ;  the  glu- 
tinous mass  does  not  hereby  pass  by  boiling  into  a  hard 
soap,  but,  after  a  sufficient  evaporation   of  the  water, 
yields  a  soft  mass  (soft  soap  or  potassa  soap).      This 
kind  of  soap  is  frequently    employed  in  print  works 
for  the  cleansing  of  colored  fabrics.    If  whale  oil,  hemp- 
seed  oil  or  linseed  oil  is  used  instead  of  olive  oil,  a  darker- 
colored  soft  soap  is  obtained,  which  is  usually  colored 
green  by  indigo  and  turmeric  (green  and  black  soap). 

Ammonia  acts  far  more  feebly  than  potassa  and  so- 
dium upon  fats.  If  some  of  the  unctuous  oils  are 
shaken  up  with  ammonia,  thick  white  mixtures,  lini- 
ments, are  obtained,  which  are  often  applied  by  friction 
to  the  skin. 

Hard  soaps  are  formed  from  fats  by  soda,  soft  soaps 
by  potassa.  The  chemical  process  taking  place  in  both 
cases  may  be  explained  as  follows. 

542.  Fat  Adds.  —  The  fats,  as  was  shown  in  §  533, 
consist  of  several  simple,  sometimes  solid,  sometimes 
fluid,  kinds  of  fat, —  among  which  the   solid  stearine 
and  the  fluid  oleine  are  especially  predominant.     These 
proximate  constituents  of  the  natural  fats  may  be  re- 


FATS    AND    FAT    OILS. 

garcled  as  saline  bodies ;  that  is,  as  combinations  of  an 
acid  with  a  base.  Every  simple  fat  contains  a  peculiar 
acid,  —  stearine,  stearic  acid  ;  oleine,  oleic  acid ;  palmi- 
tine,  palmitic  acid,  &c. ;  but  all  contain  one  and  the 
same  base,  to  which  the  name  oxide  of  glyceryle  (sweet 
principle  of  oil)  Jhas  been  given. 

Stearine  is,  accordingly,  stearate  of  oxide  of  glyceryle. 
Oleine     "          "  oleate  of  oxide  of  glyceryle. 

rp  i  j         u          u          C  a  mixture  of  much  stearate,  and  a  little  oleate 
(        of  oxide  of  glyceryle,  &c. 

To  designate  the  different  acids  contained  in  the  fats, 
the  general  term  "fat  acids"  will  always  be  used  in 
the  following  pages.  Fats  in  general  are  accordingly 
to  be  regarded  as  combinations  of  fat  acids  with  oxide 
of  glyceryle)  or  as  salts  of  fat  acids  and  oxide  of  gly- 
ceryle. 

543.  The  process  of  the  formation  of  soap  is  thus  one 
of  simple  elective  affinity ;  the  stronger  bases,  soda  and 
potassa,  displace  the  weaker  oxide  of  glyceryle,  and 
combine  with  the  fat  acids,  forming  compounds  of  fat 
acids  with  soda  (soda  soap),  or  of  fat  acids  with  potassa 
(potassa  soap).  From  potassa  and  fat  acids  with  ox- 
ide of  glyceryle  are  formed  fat  acids  with  potassa  and 
free  oxide  of  glyceryle  (potassa  soap).  From  soda  and 
fat  acids  with  oxide  of  glyceryle  are  formed  .fat  acids 
with  soda  and  free  oxide  of  glyceryle  (soda  soap). 

In  the  first  two  experiments  the  separated  oxide  of 
glyceryle,  soluble  in  water,  remains  in  the  under  lye  ; 
but  in  the  soft  soap,  when  the  surplus  of  water  does  not 
separate  as  a  fluid  from  the  soap,  but  is  removed  by 
evaporation,  it  remains  mechanically  mixed  with  the 
soap. 

The  action  of  common  salt  may  be  seen  by  try- 
ing to  dissolve  hard  soap  in  salt  water;  no  solution 


550  VEGETABLE    MATTER. 

takes  place,  not  even  on  boiling,  for  soap  is  insoluble  m 
salt  water,  and  likewise  in  strong  lye;  therefore,  soap 
may  be  precipitated  from  a  solution  in  water  by  the 
addition  of  common  salt.  This  method  of  separation 
is  usually  employed  on  a  large  scale,  since  it  yields  a 
purer  soap  than  when  the  water  is  removed  by  evapo- 
ration ;  for,  in  the  latter  case,  hydrated  oxide  of  gly- 
ceryle,  surplus  of  lye,  and  perhaps,  also,  some  impurities 
contained  in  the  lye  or  fat,  remain  mixed  with  the  soap, 
while  by  the  former  method  they  are  dissolved  in  the 
liquid  (under  lye). 

544.  Conversion  of  Potassa  Soap  into  Soda  Soap.  — 
Experiment.  —  Dissolve  some  of  the  soft  soap  obtained 
in  §  541  in  boiling  water,  and  sprinkle  in  some  salt; 
the  soap  separates,  and  collects  upon  the  surface  of  the 
water,  yet,  when  cold,  it  will  no   longer  be  soft,  but 
hard.     The  salt  here  acts  in  another  manner ;  it  occa- 
sions an  interchange  of  the  constituent  parts ;  namely, 
from  fat  acids  with  potassa  and  chloride  of  sodium  are 
formed  chloride  of  potassium  and  fat  acids  with  soda 
(soda  soap). 

Soap-makers  often  proceed  in  this  way  on  a  large 
scale ;  they  make  a  caustic  potassa  lye  of  wood-ashes 
and  lime  (lye  of  wood-ashes),  boil  it  with  fat,  and  final- 
ly convert  the  soft  potassa  soap  obtained  into  hard 
soda  soap,  by  means  of  common  salt. 

SOAP  AND  ACIDS. 

545.  Experiment.  —  Dissolve  some  of  the  hard  soda 
soap  in  hot  water,  and  add  to  it  vinegar  by  drops  until 
a  turbidness  ensues.     Vinegar,   and   other   acids,    are 
stronger  than  the  fat  acids ;  therefore,  they  withdraw 
from  the   latter   the   base,  and  the   fat   acids    are   set 


FATS    AND    FAT    OILS.  551 

free.  As  these  are  lighter  than  water,  and  at  the  same 
time  insoluble  in  it,  so  they  collect  on  the  surface  of 
the  water.  The  fat  acids  thus  obtained  resemble  tal- 
low externally,  but  it  is  evident  that  they  are  not  tal- 
low, since,  even  after  long  washing,  they  still  have  an 
acid  reaction,  which  is  not  the  case  with  tallow,  and 
they  are  easily  dissolved  in  hot  alcohol,  but  tallow  very 
difficultly.  Three  fourths  of  the  mass  consists  of  stearic 
acid,  one  fourth  of  oleic  acid.  When  strongly  pressed 
between  blotting-paper,  the  oleic  acid  soaks  into,  the 
paper,  and  the  stearic  acid  remains  behind. 

Stearic  acid  is  harder  and  more  brittle  than  wax, 
brilliantly  white,  translucent,  and  melts,  at  the  tempera- 
ture of  70°  C.     There  are  now  large  factories  for  the 
preparation  of  it,  and  it  is  used  in  the  manufacture  of 
the  stearine  candles,  which  have  become  so  popular. 
Experiment.  —  Heat  some  ounces  of  strong  alcohol 
in  a  water-bath,  and  when  it  boils,  add 
to  it  as  much  stearic  acid  as  will  dis- 
solve in  it.     Pour  half  of  the  solution 
obtained  into  cold  water,  and  let  the 
other  cool  quietly  ;  in  the  former  case 
the  stearic  acid  is  obtained  as  a  light, 
silky,  brilliant  mass,  while  in  the  latter 
it  takes  the  form  of  delicate  crystal- 
line plates. 

546.  Experiment.  —  If  an  acid  is  added  to  a  solution 
of  oil-soap,  an  oily  fluid  separates,  which  consists  prin- 
cipally of  oleic  acid. 

Oleic  acid  in  its  external  appearance  is  hardly  to  be 
distinguished  from  olive  oil,  but  it  differs  from  it  in  the 
following  respects  :  it  has  an  acid  taste  and  reaction, 
which  olive  oil  has  not,  and  it  readily  dissolves  even 
in  cold  alcohol,  while  olive  oil  does  not.  The  oleic  acid, 


552  VEGETABLE    MATTER. 

procured  in  stearic-acid  factories  from  tallow,  as  a  sec- 
ondary product,  now  frequently  occurs  in  commerce, 
and  on  account  of  its  cheapness  is  employed  in  the 
manufacture  of  soap,  and  in  greasing  wool  for  spinning. 

547.  Oxide  of  glyceryle  (glycerine,  or  sweet  principle 
of  oil).  —  Experiment.  —  Add  to  the  soft  soap,  prepared 
according  to  §  541,  a  solution  of  tartaric  acid,  and 
leave  the  watery  fluid,  after  being  clarified  by  filtration, 
to  evaporate  in  a  warm  place.  The  saline  mass  re- 
maining after  evaporation  consists  of  bitartrate  of 
potassa  (tartar)  and  of  the  base  of  the  fats,  oxide  of 
glyceryle ;  when  strong  alcohol  is  added,  the  latter  dis- 
solves, while  the  bitartrate  of  potassa,  together  with 
any  excess  of  tartaric  acid  that  may  be  present,  re- 
mains undissolved. 

The  oxide  of  glyceryle,  which  remains  after  the 
evaporation  of  the  alcohol,  has  the  appearance  of  a  yel- 
low syrup.  It  has  not  an  alkaline  taste,  but  is  sweet, 
like  sugar ;  neither  does  it  react  basically,  although  it  is 
soluble  in  water.  It  has,  accordingly,  no  similarity  to 
other  bases  soluble  in  water,  as,  for  example,  potassa  or 
soda.  But  the  reason  why  it  is  regarded  as  a  base  is 
evident  from  its  behaviour  with  acids ;  it  is  considered 
as  a  base,  because  it  combines  with  acids  in  fixed  pro- 
portions, forming"  compounds  having  the  character  of 
salts.  It  constitutes  only  about  a  tenth  or  twelfth  part 
of  fats ;  an  ounce  and  a  quarter  of  it,  at  most,  is  con- 
tained in  one  pound  of  tallow. 

Experiment.  —  Wipe  the  bowl  containing  the  small 
quantity  of  the  oxide  of  glyceryle  that  has  been  ob- 
tained with  white  blotting-paper,  and  heat  the  latter  in 
a  spoon.  During  the  combustion  there  will  be  evolved 
from  it  an  extremely  pungent  odor,  proceeding  from  the 
oxyde  of  glyceryle,  which  is  decomposed  by  the  heat 


FATS    AND    FAT    OILS.  553 

intt  a  volatile,  extremely  pungent  substance  (acrolcine 
or  o'Me  of  aery le),  which  causes  lachrymation.  Hence 
is  explained  the  pungent  odor  which  is  perceived  dur- 
ing the  imperfect  combustion  of  all  kinds  of  fat.  This 
odor  is  very  strikingly  manifested,  also,  when  varnished 
articles  are  drying ;  for  instance,  in  the  drying  chambers 
of  the  oil-cloth  factories.  This  volatile  matter  may  be 
formed  also,  even  at  a  low  temperature,  from  glycerine. 
No  smell  of  acroleine  is  evolved  on  heating  the  pure 
fat  acids. 


PROPERTIES  OF  SOAPS. 

548.  Washing-  ivith  Soaps.  —  Soaps  have  two  impor- 
tant properties ;  —  1st,  they  dissolve  fat  and  oils  ;   2d, 
they  are  very  easily  resolved,  merely  by  mixing  with 
much  water,  into  an  acid  salt  and  free  alkali ;  the  latter 
dissolves,  as  is  well  known,  most  organic  substances, 
but  the  former  effects  by  its  lubricity  an  easy  washing 
away   of  the  dissolved  matter  from  other  substances. 
On  these  two  properties  depends  the   application   of 
soap  in  washing.     The  separated  acid  salt  of  fat  acids 
with  alkali   modifies  at  the  same  time  the   action   of 
the  free  alkali,  and  keeps  the  articles  pliant  whicli  are 
washed  with  soap,  while    they   would   become   rigid 
if  they  were  cleansed  with  caustic  alkalies  alone.     To 
prevent  the  shrinking  of  woollen  articles,  wash  them 
with  a  weak  solution  of  carbonate  of  soda,  instead  of 
with  soap. 

549.  Soap   and  Alcohol.  —  Experiment.  —  Pour   one 
ounce  of  alcohol  upon  one  ounce  of  the  shavings  of 
tallow  soap ;  the  soap  is  completely  dissolved  on  heat- 
ing in  the  water-bath,  but  the  solution  congeals  on  cool- 
ing to  a  transparent  jelly.     This  jelly-like  soap,  mixed 

47 


554  VEGETABLE    MATTER. 

with  camphor  and  ammonia,  is  called  opodeldoc.  The 
white  stars  separating  from  this  consist  of  crystallized 
stearate  of  soda.  All  soaps  prepared  from  solid  fats 
(rich  in  stearine)  behave  lijie  tallow  soap. 

Experiment.  —  Dissolve  one  dram  of  Naples  soap  in 
half  an  ounce  of  alcohol ;  this  solution  does  not  coagu- 
late on  cooling;  it  forms  the  tincture  of  soap.  By 
evaporation,  a  diaphanous  soap  is  obtained  (transparent 
soap).  All  the  soaps  made  from  the  fluid  fats  (rich  in 
oleine)  act  like  the  Naples  soap. 

550.  Insoluble  Soaps.  —  Experiment.  —  If  some  lime- 
water  is  added  to  a  solution  of  soap  in  water,  a  pre- 
cipitate of  insoluble  lime  soap  is  formed ;  hence  is  ex- 
plained why  spring-water,  which  generally  contains 
lime  (hard  water),  neither  dissolves  soap  nor  lathers 
with  it,  and  accordingly  cannot  be  used  for  washing. 

Experiment.  —  By  adding  acetate  of  lead  (§  337)  to  a 
solution  of  Naples  soap  in  hot  water,  as  long  as  a  pre- 
cipitate is  formed,  we  obtain,  by  double  elective  affinity, 
acetate  of  soda,  which  remains  dissolved,  and  a  com- 
pound of  fat  acid  with  oxide  of  lead,  which  separates 
as  a  white,  adhesive  mass,  that  may  be  kneaded  with 
the  moist  hands,  and  formed  into  rolls  (lead  soap  or 
lead  plaster).  From  the  compound  of  fat  acid  and 
soda,  and  from  the  acetate  of  lead,  are  formed  a  com- 
pound of  fat  acid  with  oxide  of  lead  (lead  plaster)  and 
acetate  of  soda. 

In  pharmaceutic  laboratories,  this  plaster,  generally 
known  under  the  name  of  diachylon,  is  prepared  in  a 
different  manner,  namely,  by  boiling  litharge  with  olive 
oil  and  some  water.  By  this  method  oxide  of  glyceryle 
is  readily  obtained,  and  in  larger  quantities,  as  a  secon- 
dary product ;  the  plaster  mad^e  has  only  to  be  washed 
with  hot  water,  and  the  water  evaporated  after  the  ox- 


VOLATILE    OILS. 

ide  of  lead  dissolved  in  it  has  been  previously  precipi- 
tated by  sulphuretted  hydrogen.  If,  instead  of  litharge^ 
white  lead  (carbonate  of  lead)  is  boiled  with  oil  and 
water,  we  likewise  obtain  a  compound  of  fat  acid  and 
oxide  of  lead,  .since  the  carbonic  acid  is  expelled  by  the 
fat  acids.  In  this  manner  the  plaster  of  carbonate  of 
lead  is  prepared,  which  has  commonly  a  whiter  color 
than  the  former  plaster,  because  it  still  contains  som- 
white  lead  mechanically  mixed  with  it. 


X.   VOLATILE    OR  ETHEREAL   OILS. 

551.    Preparation  of  Volatile   Oils.  —  Experiment. — 
Put  one  ounce  of  turpentine  in  a  dish  in  a  warm  place, 


Fig.  210. 


and  when  it  has  become  liquid  transfer  it  to  a  capacious 
flask,  pour  upon  it  four  ounces  of  ^ater,  and  distil  until 

about  three  fourths  of  the  water  has <  passed  over.    Pour 

• 

the  residue,  while  still  hot,  into  cold  water,  in  which 
the  non-volatile  portion  of  the  turpentine  remaining 


556  VEGETABLE    MATTER. 

behind  congeals  to  a  solid  mass  (resin).  A  strong* 
smelling,  colorless  liquid,  a  volatile  oil,  commonly 
known  under  the  name  of  oil  of  turpentine,  floats  on 
the  surface  of  the  water  distilled  over.  Turpentine, 
a  juice  which  exudes  from  pines,  larches,  and  other 
trees,  when  the  inner  bark  is  cut  through,  is  accord- 
ingly a  mixture  of  resin  and  oil  of  turpentine  ;  the 
latter  is  converted  by  heat,  simultaneously  with  the 
water,  into  steam,  and  on  cooling  is  again  condensed 
to  a  liquid. 

Experiment.  —  Distil  in  the  same  manner  half  an 

Fig.  211.  ounce    of   cum" 

in-seeds    (which 

have  been  pre- 
viously bruised 
in  a  mortar),  in 
a  retort  contain- 
ing four  ounces 
of  water,  until 
two  ounces  of 
water  have  passed  over.  The  drops  floating  upon  the 
water  are  likewise  a  volatile  oil,  oil  of  cumin;  they 
have  the  smell  and  taste  of  the  cumin-seeds,  but  in  a 
stronger  degree,  while  the  residue  remaining  in  the  re- 
tort has  scarcely  the  least  smell  or  taste  of  them.  All 
volatile  oils  possess  a  burning  taste,  and  are  somewhat 
harsh  to  the  touch ;  but  the  fat  oils  have  a  mild  taste 
and  an  unctuous  feeling. 

DIFFERENT  KINDS   OF  VOLATILE  OILS. 

552.  Whenever  we  perceive  an  odor  in  a  plant,  we 
may  presume  that  a  volatile  oil  is  present,  which  grad 
ually  evaporates.  But  how  incredibly  diffused  and 


VOLA  TILE    OILS.  55? 

liluted  this  must  be  in  many  plants  may  be  inferred 
from  the  fact,  that  scarcely  a  quarter  of  an  ounce  of  vol- 
atile oil  is  contained  in  one  hundred  pounds  of  fresh 
roses,  or  orange  blossoms.  We  most  frequently  find 
the  volatile  oils*  in  the  flowers  and  seeds,  sometimes  in 
the  stalks  and  leaves,  but  more  rarely  in  the  roots 
They  are  obtained  almost  in  the  same  way,  without 
exception,  as  oil  of  turpentine,  by  distilling  the  vege- 
table parts  with  water.  The  oils  procured  from  the 
skins  and  peels  of  some  fruits,  as  the  oil  of  lemons,  and 
bergamot,  contained  in  the  rind  of  lemons,  citrons, 
and  oranges,  form  an  exception,  since  such  oils  are  ob- 
tained by  expression  from  the  fresh  rind. 

553.  Of  the  more  known  volatile  oils  we  obtain,  — 

a.)  From  the  flower  :  — 

Oil  of  roses,  a  yellowish,  thick  fluid,  with  flakes  re- 
sembling tallow  floating  in  it. 

Oil  of  orange-flowers  (ol.neroli),  colorless,  reddish  in 
the  light ;  contains  no  oxygen. 

Oil  of  camomile,  a  dark  blue,  thick  liquid ;  becomes 
green,  and  finally  brown,  by  age  and  light. 

Oil  of  lavender,  a  yellowish,  thin  liquid. 

Oil  of  cloves,    yellowish,  soon  becomes   brown;   a 
somewhat  thick  fluid,  heavier  than  water. 

b.)  From  seeds  and  fruits  :  — 

Oil  of  cumin,  colorless;  becomes  yellowish,  and  final- 
ly brown,  by  age. 

Oil  of  anise-seed,  yellowish  ;  congeals  even  at  12°  C. 

Oil  of  fennel,  colorless  or  yellowish ;  congeals  like- 
wise readily. 

Oil  of  dill,  yellow ;  becomes  brown  in  the  light. 

Oil  of  nutmeg-,  a  pale  yellow,  thin  liquid,  has  the 
smell  of  nutmegs. 

Oil  of  bitter  almonds,  yellow:  heavier  than  water; 
47* 


558  VEGETABLE    MATTER. 

contains  prussic  acid,  and  consequently  is   very  pot 
sonous. 

Oil  of  mustard,  yellowish,  of  an  extremely  pungent 
smell,  causing  lachrymation ;  contains  sulphur. 

Oil  of  juniper,  colorless ;  contains  no  oxygen. 

Laurel  oil,  white  or  yellow ;   a  thick  fluid. 

Oil  of  savin,  colorless  or  yellowish  ;  a  thin  fluid  ;  con- 
tains no  oxygen. 

Oil  of  parsley,  pale  yellow;  on  being  shaken  with 
water,  separates  into  a  light  volatile  oil,  and  into  a 
heavy,  solid,  crystalline  oil. 

Oil  of  lemons,  from  lemon-peels,  contains  no  oxygen. 

Oil  of  orange-peel  likewise  contains  no  oxygen. 

Oil  of  bergamot,  from  the  rind  of  the  bergamot 
orange,  a  pale  yellow,  very  thin  liquid. 

c.)  From  the  leaves  and  branches :  — 

Oil  of  the  curled  leaf  mint  (Mentha  crispa),  colorless 
or  yellowish  ;  becomes  brown  with  age. 

Oil  of  peppermint,  colorless  or  yellowish,  a  very  thin 
liquid,  now  frequently  exported  to  Europe  from  Amer 
ica. 

Oil  of  balm,  pale  yellow,  has  an  odor  like  that  of 
lemons. 

Oil  of  marjoram,  yellowish  or  brownish. 

Oil  of  thyme,  when  fresh,  yellowish  or  greenish  ;  when 
old,  brownish-red. 

Oil  of  sage,  when  fresh,  yellowish  or  greenish ;  when 
old,  brownish-red. 

Oil  of  wormwood,  dark  green ;  soon  becomes  brown 
or  yellow,  and  viscous  in  the  light. 

Oil  of  rosemary  (ol.  anthos),  colorless  and  very  thin, 
is,  next  to  the  oil  of  turpentine,  the  cheapest  volatile 
oil. 

Oajeput  oil,  from  the  leaves  of  a  tree  growing  in  tha 


VOLATILE    OILS.  559 

Moluccas ;  the  oil,  when  pure,  is  colorless ;  the  crude 
oil  is  commonly  green,  and  often  contains  camphor ;  it 
has  a  camphorated  odor. 

Oil  of  rue,  pale  yellow,  or  greenish. 

Oil  of  cinnainon,  yellow  ;  soon  becomes  brown  in  the 
air ;  heavier  than  water. 

Oil  of  turpentine,  the  most  common  of  the  volatile 
oils,  is  contained  in  all  our  fir-trees,  and  exudes  from 
them,  mixed  with  resin,  as  turpentine  (§  568).  When 
purified,  it  is  colorless  and  thin,  and  has  an  agreeable, 
penetrating  odor ;  it  contains  no  oxygen.  An  ordinary 
sort,  possessing  a  disagreeable  empyreumatic  odor,  ob- 
tained in  the  preparation  of  pitch  from  pine  resin,  is 
crude  oil  of  turpentine. 

Camphor  occurs  in  commerce  as  a  solid  white,  crys- 
talline, odoriferous  mass,  prepared  by  distillation  with 
water,  or  by  sublimation  from  the  wood  of  the  camphor- 
tree,  growing  in  Japan  and  the  East  Indies. 

d.)  From  roots  :  — 

Oil  of  acorus,  yellow  or  brownish. 

Oil  of  valerian,  pale  yellow,  or  greenish ;  becomes 
rapidly  brown  and  viscous  on  exposure  to  the  air. 

It  is  very  remarkable,  that  we  sometimes  find  several 
sorts  of  oil  in  one  and  the  same  plant.  Thus,  for  ex- 
ample, we  find  in  the  orange-tree  three  different  kinds 
of  oil ;  one  in  the  leaves,  another  in  the  blossom,  and  a 
third  in  the  rind  of  the  fruit. 

554.  Ferment  Oils.  —  Experiment.  —  If  water  is 
poured  on  the  centaury-plant  (Erythrsea  centaurium), 
and  it  is  left  in  a  warm  place  until  fermentation  com- 
mences, a  very  penetrating  odor  is  evolved  from  the 
\eaves,  which  were  previously  scentless ;  the  odor  pro* 
ceeds  from  a  volatile  oil,  which  was  generated  during 
the  fermentation.  In  a  similar  manner,  the  fresh,  scent- 


560  VEGETABLE    MATTER. 

*ess  leaves  of  the  tobacco-plant  obtain  the  well-known 
nicotian  odor  by  the  so-called  sweating  process.  Oils 
of  this  kind,  which  may  be  generated  by  fermentation 
from  many  other  odorless  plants,  are  called  ferment  oils. 
In  the  brandy-distilleries  there  is  evolved  also,  on  the 
fermentation  of  potatoes  and  grain,  a  disagreeably- 
smelling  oil  (fusel  oil))  which  partly  distils  over  with 
the  brandy  or  spirit,  and  imparts  to  these  liquids  the 
fusel  taste  and  smell.  On  filtering  through  charcoal,  it 
remains  behind  in  the  pores  of  the  latter. 

555.  Empyreumatic  Oils.  —  Finally,  oily  volatile  sub- 
stances are  produced  by  the  dry  distillation  of  vegetable 
and  animal  matter ;  for  instance,-  oil  of  wood-tar  from 
wood,  coal  oil  from  pit-coal,  animal  oil  from  bones,  oil 
of  amber  from  amber,  &c.     They  are  all  distinguished 
by  an  exceedingly  disagreeable  odor,  and  are  mixtures 
of  various  volatile  substances.     They  are  called  empy- 
reumatic  oils. 

Rock  oil)  or  petroleum  (neTpos,  rock),  is  of  a  similar 
nature ;  it  oozes  out  from  the  earth  in  many  places  in 
Asia,  where  it  is  formed  in  a  manner  as  yet  unknown 
to  us.  The  red  color  of  the  oil  occurring  in  commerce 
is  given  to  it  by  the  addition  of  alkanet-root. 

PROXIMATE  CONSTITUENTS  OF  THE  VOLATILE  OILS. 

556.  All  these   oils  are  volatile   at  average  temper- 
atures, except  camphor,  which  begins  to  melt  at  the 
temperature  of  175°  C. ;   but  below  this  temperature 
forms  a  white,  solid,  crystalline  mass.     If  the  volatile 
oils  are  cooled,  there  is  frequently  separated  from  them 
a  beautifully  crystallized,  solid,  white,  camphor-like  sub- 
stance, which  has  been  called  stearoptene^  in  opposition 
to  the  liquid  portions  that  remain,  which  are  called 


VOLATILE    OILS.  561 

eleoptene.  Accordingly,  the  volatile  oils,  like  the  fats, 
consist  of  two  proximate  constituents,  one  of  \vhich 
may  be  regarded  as  solid  and  crystallized,  but  the  other 
only  as  a  liquid.  Many  oils  —  for  instance,  the  oils  of 
rose  and  anise-fieed  —  are  so  rich  in  stearoptene,  that, 
when  kept  in  cool  cellars,  they  congeal  into  a  nearly 
solid  mass. 

ELEMENTARY  CONSTITUENTS  OF  THE  VOLATILE  OILS. 

557.  The  volatile  oils  are  divided  into  three  classes, 
according  to  the  elements  of  which  they  are  com- 
posed :  — 

a.)  Into  the  non-oxygenated  oils  (having  two  ele- 
ments) ;  these  consist  only  of  carbon  and  hydrogen 
(C,  H),  so  that  they  may  be  regarded  as  condensed  il- 
luminating-gas. To  this  class  belong  rock  oil  and  oils 
of  turpentine,  juniper,  savin,  lemons,  &c. 

b.)  Into  oxygenated  oils  (having  three  elements), 
which,  beside  carbon  and  hydrogen,  contain  also  oxy- 
gen (C,  H,  O);  most  of  the  other  volatile  oils  have 
this  constitution. 

c.)  Into  sulphuretted  oils,  which  are  composed  of 
carbon,  hydrogen,  and  sulphur  (sometimes  with  and 
sometimes  without  nitrogen).  The  oils  of  this  class  are 
distinguished  by  a  very  pungent  smell,  causing  lachry- 
mation,  and  by  a  great  acridity,  raising  blisters  on  the 
skin  when  brought  in  contact  with  it.  The  oils  of 
mustard,  horseradish,  scurvy-grass,  garlic,  hops,  (fee. 
belong  to  this  class. 

Of  these  elements,  hydrogen  (as  regards  the  number 
of  atoms)  commonly  predominates ;  hence,  the  volatile 
oils  are  usually  reckoned  among  the  organic  substances 
rich  in  hydrogen. 


562  VEGETABLE    MATTER. 

PROPERTIES  OF  THE  VOLATILE  OILS. 

558.  Experiment.  —  Pour  a  drop  of  some  volatile  oL 
upon  a  sheet  of  paper,  and  let  it  remain  exposed  to  the 
air :  the  paper  at  first  receives  an  apparent  grease-spot, 
but  this  disappears  after  a  time,  because  the  oil  gradu- 
ally evaporates.     The  name  volatile  or  ethereal  oil  thus 
explains  itself;  and  the  disappearance  of  camphor,  on 
being  exposed  to  the  air,  is  owing  to  this  volatileness. 

If  the  oiled  paper  is  placed  upon  a  warm  stove,  the 
evaporation  takes  place  much  more  rapidly.  Aromatic 
oils  are  employed  in  this  way  for  perfuming  apartments. 
Usually  a  quantity  of  flowers,  wood,  and  rinds,  finely 
cut  up,  are  moistened  with  the  oil,  and  scattered  as  a 
fumigating  powder  upon  the  stove. 

559.  Experiment.  —  Heat  a  quarter  of  an  ounce  of 
oil  of  turpentine  in  a  vessel  to  boiling.     A  thermometer 
introduced  into  the  liquid  will  indicate  a  temperature 
of  about   150°  C. ;    oil   of    turpentine   accordingly  re- 
quires half  as  much  again  heat  for  boiling  as  water. 
Other  oils  often  boil  with   even  more  difficulty.     The 
vapor  may  be  inflamed  by  a  taper,  when  it  will  burn 
with  an  intense  sooty  flame ;  it  is  easily  extinguished 
by  covering  the  vessel  with  a  board,  but  water  must  on 
no  account  be  employed  for  extinguishing  burning  oils. 
Then  remove   the  oil  from  the  fire ;   after  it  is  cold, 
mix  it  with  some  water,  and  again  heat  it ;  as  long  as 
any  water  is  present,  the  temperature  of  the  fluid  will 
not  rise  above  100°  C.     The  ascending  vapor  is  a  mix- 
ture of  aeriform  water  and  aeriform  oil.     The  same 
thing  occurs  here  as  previously  mentioned ;  the  less  vol- 
atile oil  evaporates  with  the  more  easily  volatile  water. 
The  oils  remain   unchanged    at  the  boiling  point  of 
water,  but  at  their  own  boiling  point  (140°  to  200°  C.) 


VOLATILE    OILS.  563 

they  become  not  unfrequently  somewhat  empyreumat- 
ic ;  this  is  the  reason  why  water  is  always  added  in 
the  preparation  of  oils,  and  also  in  the  redistillation  of 
them  (rectification). 

560.  Experiment.  —  Inflame  some  drops  of  oil  of  tur- 
pentine put  upon  a  shaving,  and  also  a  piece  of  cam- 
phor laid  upon  water ;  both  bodies  will  ignite,  and  burn 
with  a  highly  luminous  and  sooty  flame.     The  volatile 
oils  are  far  more  easily  combustible   than  the  fat  oils, 
which  in  order  to  burn  with  a  flame  must  be  heated  to 
350°  C.     We  have  consequently  in  oil  of  turpentine  a 
convenient   means  for  speedily  lighting  oil-lamps ;    it 
being  merely  necessary  to  smear  the  wick  with  a  few 
drops  of  it. 

Experiment.  —  Pour  a  mixture  of  half  an  ounce  of 
absolute  alcohol  with  half  a  dram  of  oil  of  turpentine 
into  a  spirit-lamp ;  the  mixture  gives,  when  lighted,  a 
strongly  illuminating,  but  no  longer  a  sooty  flame, 
since  all  the  carbon  of  the  oil  of  turpentine  is  convert- 
ed by  the  heat  of  the  burning  alcohol,  rich  in  hydrogen, 
into  illuminating  gas,  and  then  into  carbonic  acid  (and 
water).  This  mixture  is  now  used  in  lamps  construct- 
ed for  the  purpose,  and  which  are  so  made  that  the 
liquid  evaporates  in  them,  and  the  vapor  ignites  as  it 
issues  from  several  small  openings. 

561.  Volatile  Oils  and  Water.  —  Experiment.  —  Drop 
some  oil  of  cumin  upon  water ;  the  oil  floats   on  the 
surface  without  mixing  with  the  water,  for  most  of  the 
volatile  oils  are  lighter  than  water ;  but  there  are  some, 
such  as  oil  of  cinnamon,  oil  of  cloves,  and  oil  of  bit- 
ter almonds,   which   are  heavier  than  water,  and  sink 
in  it. 

If  the  mixture  is.  briskly  shaken,  the  water  becomes 
*urbid,  because  the  oil  is  thus  divided  into  small,  invis- 


564  VEGETABLE    MATTER. 

ible  globules,  which  are  kept  suspended  in  the  water. 
The  water  may  be  again  clarified  by  filtration,  but  it 
retains  the  smell  and  taste  of  the  oil,  since  a  small 
quantity  of  it  remains  dissolved.  Many  such  solutions 
are  kept  in  the  apothecaries'  shops,  under  the  name  of 
medicated  or  distilled  waters.  It  is  well  to  keep  them 
protected  from  the  light,  and"  in  full  vessels,  —  both 
light  and  air  having  a  decomposing  action  on  the  vol- 
atile oils.  They  are  commonly  prepared  by  distilling 
with  water  the  vegetable  substance  containing  the  oil, 
as  thereby  a  more  intimate  combination  of  the  water 
with  the  oil  is  effected  than  by  merely  shaking  it  up. 

562.  Volatile  Oils  and  Alcohol  —  Experiment.  — 
Add  a  drop  of  oil  of  cumin  to  one  ounce  of  strong 
alcohol ;  it  dissolves  readily  and  entirely.  All  the  vol- 
atile oils  are  soluble  in  alcohol,  most  of  them  in  alco- 
hol of  eighty  per  cent. ;  but  the  non-oxygenated  oils, 
such  as  oil  of  turpentine,  oil  of  lemons,  &c.,  only  in 
absolute  alcohol.  If  an  ounce  of  water,  in  which  half 
an  ounce  of  sugar  has  previously  been  dissolved,  is 
added  to  the  solution,  we  obtain  cumin-cordial.  In 
this  manner,  by  the  aid  of  various  aromatic  Oils,  the  in- 
numerable cordials  occurring  in  commerce  are  now  gen- 
erally prepared  (preparation  of  cordial  in  the  cold  way). 
They  were  formerly  manufactured  from  aromatic  seeds, 
flowers,  herbs,  &c.,  by  pouring  brandy  over  them,  the 
brandy  being  afterwards  distilled  or  drawn  off,  where- 
by a  spirituous  solution  of  volatile  oils  was  likewise 
obtained. 

Experiment.  —  If  some  drops  of  bergamot,  orange- 
flower,  lavender,  or  rosemary  oils  are  dissolved  in  half 
an  ounce  of  strong  alcohol,  we  obtain  a  spirit  of  a  very 
pleasant  odor.  In  a  similar  way  the  innumerable 
kinds  of  perfumed  waters  are  prepared,  at  the  head  o* 


VOLATILE    OILS.  563 

which  stands  the  well-known  eau  de  Cologne.  The 
fumigating  spirit  also,  which,  instead  of  the  fumigating 
powder,  is  often  sprinkled  on  a  warm  stove,  has  a 
similar  composition.  Camphor  spirit,  much  used  as 
an  external  rejnedy,  is  likewise  a  solution  of  camphor 
in  alcohol. 

563.  The  volatile  oils  are  not  only  dissolved  by  al- 
cohol, but  also  by  ether  and  concentrated  acetic  acid. 
A  solution  of  oil  of  cloves,  cinnamon,  bergamot,  and 
thyme,  in  acetic  acid,  is  used  as  a  perfumed  vinegar,  on 
account  of  its  refreshing  odor. 

The  volatile  oils  may  also  be  mixed  with  fat  oils, 
and  with  some  kinds  of  tallow  and  lard ;  hence  by 
means  of  them  an  agreeable  odor  may  be  imparted  to 
the  latter,  as,  for  instance,  in  hair  oils,  pomatum,  &c.,  or 
grease-spots  be  dissolved  and  removed  by  them  from 
various  articles.  Volatile  oils  mixed  with  alcohol  yield, 
when  shaken  up  with  olive  oil,  a  turbid,  milky  liquid, 
because  the  alcohol  does  not  dissolve  the  olive  oil ;  this 
behaviour  may  be  taken  advantage  of  for  testing  the 
purity  of  mercantile  oils. 

564.  Experiment.  —  Rub  a  piece  of  sugar  some  time 
on  the  rind  of  a  fresh  lemon  ;  the  hard  sugar  tears  the 
cells  in  which  the  oil  of  lemons  is  inclosed,  and  the  oil 
is  attracted  into  the  pores  of  the  sugar.     This,  when  re- 
duced to  powder,  is  called  oleo-saccharum.     Such  mix- 
tures are  commonly  prepared  in  pharmacy  by  triturat- 
ing together  powdered  sugar  and  volatile  oils. 

565.  Experiment.  —  If  you  add  some  drops  of  oil  of 
turpentine  to  iodine,  a  brisk  emission  of  sparks  ensues, 
since  a  part  of  the  hydrogen  is  expelled  and  replaced 
by  the  iodine.     The  same  phenomenon  is  occasioned 
by  all  non-oxidized  oils,  but  not  by  the  oxidized ;  there- 
lore  iodine  may  serve  as  a  test,  although  not  a  very 

48 


566  VEGETABLE    MATTER. 

accurate  one,  for  ascertaining  whether  oils  of  the  lat- 
ter class  have  been  adulterated  with  oil  of  turpentine. 

566.  Conversion  of  the  Volatile  Oils  into  Resins.  — 
Experiment.  —  Let  some  oil  of  turpentine  remain  ex- 
posed to  the  air  for  some  weeks,  in  a  cup  covered  with 
paper,  and  afterwards  put  the  cup  in  a  warm  place  to 
evaporate  the  oil ;  it  will  not  entirely  volatilize,  but 
will  leave  at  first  a  viscous,  and  afterwards  a  vitreous 
residue.  This  residue  is  resin.  All  volatile  oils  are 
converted  into  resin,  because  they  gradually  absorb  oxy- 
gen from  the  air  ;  which,  as  in  the  case  of  the  transfor- 
mation of  alcohol  into  vinegar,  first  combines  with  a 
portion  of  the  hydrogen  of  the  oil,  forming  water,  and 
then  unites  with  the  oil  itself.  Alcohol,  on  exposure 
to  the  air,  is  converted  by  the  removal  of  hydrogen  into 
aldehyde,  then  by  the  reception  of  oxygen  into  acetic 
acid ;  the  volatile  oils  are,  in  a  similar  manner,  first  con- 
verted by  the  air  into  turpentine  (mixtures  of  volatile 
oils  and  resin),  and  then  into  resins.  Oil  of  turpentine 
consists  of  Cio  Hie ;  resin,  of  Clo  H15  O  ;  consequently  the 
former  has  only  to  relinquish  one  atom  of  hydrogen, 
and  receive  one  atom  of  oxygen,  to  be  converted  into 
resin.  This  explains  very  simply  why  the  volatile  oils 
become  gradually  viscous  and  scentless  on  being  kept, 
and  more  rapidly  in  large  and  only  partially  filled  bottles 
than  in  small  ones,  and  why  the  drops  running  down 
on  the  outside  of  the  bottles  dry  up  first  into  a  sticky, 
and  then  into  a  resinous  mass.  Old  oil  of  turpentine 
is,  for  this  reason,  not  suitable  for  removing  grease- 
spots  ;  it  dissolves,  indeed,  the  fat  or  resin  dried  into 
the  material,  but  leaves  behind  new  spots  of  resin  in 
their  place. 

The  volatile  oils  are  very  rapidly  changed  by  nitric 
acid  into  non-volatile  resinous  substances.  There  are 


RESINS    AND    GUM-RESINS.  66? 

sometimes  simultaneously  formed,  in  this  case,  peculiar 
organic  acids  ;  for  example,  turpentinic  acid  from  oil  of 
turpentine,  camphoric  acid  from  camphor,  &c.  Many 
such  acids  are  also  spontaneously  generated  together 
with  resin,  by  long  standing  in  the  air ;  for  instance, 
cinnamic  acid  in  the  oil  of  cinnamon ;  or  are  found  al- 
ready formed  in  the  volatile  oils ;  as,  for  instance,  cary- 
ophyllic  acid  in  oil  of  cloves,  &c. 

567.  Metallic  arsenic  has  no  smell ;  neither  has  ar- 
senious  acid  (arsenic  combined  with  oxygen).  We  per- 
ceive the  striking  odor  like  that  of  garlic  only  at  the 
very  moment  when  the  arsenic  is  combining  with  the 
oxygen.  The  same  thing  seems  to  happen  with  regard 
to  the  odor  of  volatile  oils,  so  that  we  may  assume  that 
the  odor  is  emitted  because  the  oils  are  combining  with 
the  oxygen  of  the  air,  and  while  they  are  combining. 
Fresh  oils,  and  those  distilled  by  exclusion  of  air,  and 
old  resinous  oils,  either  do  not  smell  at  all,  or  emit 
quite  an  unusual  odor. 


XL   RESINS   AND    GUM-RESINS   (RESIN*  ET 
GUMMI-RESINJE). 

568.  Turpentine  and  Balsams.  —  Whoever  has  been 
in  a  forest  of  fir  or  pine  trees  must  certainly  have  no- 
ticed the  yellow,  transparent  juice,  having  the  consis- 
tency of  honey,  which  exudes  from  these  trees,  and  he 
may  perhaps  have  observed  also  that  it  sticks  to  the 
fingers,  and  cannot  be  washed  off  again  by  mere  water 
This  juice  is  turpentine.  It  is  procured  in  large  quan- 
tities by  incisions  made  in  the  trees.  That  obtained 
the  European  fir-trees  is  turbid,  and  has  a  thick 


568  VEGETABLE    MATTER. 

consistency ;  it  is  called  common  European  turpentine  . 
but  Venice  turpentine  is  the  more  transparent  and  more 
fluid  sort,  which  is  procured  from  larch-trees.  A  yet 
finer  quality,  yielded  by  the  American  silver-fir,  is  called 
Canada  balsam. 

The  term  balsam  is  applied  also  to  several  other  res- 
inous vegetable  juices,  which  exude  from  some  tropi- 
cal trees,  or  are  boiled  out  from  them.  The  best  known 
are  the  yellowish  balsam  of  copaiba,  an  important  med- 
icine, the  blackish-brown  balsam  of  Peru,  and  the 
brownish-gray  balsam  of  storax  (liquid  storax),  the  last 
two  of  which  are  generally  used  for  fumigating,  on  ac- 
count of  their  agreeable  odor,  which  resembles  that  of 
vanilla. 

All  these  turpentines  and  balsams  are  to  be  regarded 
as  solutions  of  resin  in  volatile  oils,  into  which  two 
constituents  they  are  separated  when  distilled  with 
water  (§  551).  The  same  thing  happens  when  they  are 
aUowed  to  stand  for  some  time  in  an  open  vessel  in  a 
warm  place,  except  that  in  this  case  the  oil  volatilizes, 
and  diffuses  itself  in  the  air. 

569.  Preparation  of  the  Resins.  —  Experiment.  — 
Spread  a  little  turpentine  upon  a  board,  and  put  the 
board  for  some  time  near  a  heated  stove ;  the  oil  of  tur- 
pentine evaporates,  but  the  resin  remains  behind  as  an 
amorphous  Brittle  mass.  In  some  countries,  incisions 
are  made  through  the  bark  of  the  pine-trees,  and  the 
turpentine  which  exudes  is  allowed  to  evaporate  on 
the  trees  themselves,  and  after  it  has  been  purified,  by 
melting  and  straining  through  a  colander,  from  the 
woody  particles  adhering  to  it,  it  is  brought  into  mar- 
ket under  the  name  of  resin,  white  pitch,  or  Burgun* 
dy  pitch.  Large  quantities  of  such  resin  are  now  ex- 
ported from  the  forests  of  America  (American  resin) 


RESINS    AND    GUM-RESINS.  569 

Two  different  operations  are  going  on  during  the  evap- 
oration of  the  turpentine  ;  a  part  of  the  volatile  oil  found 
in  it  evaporates,  and  occasions  the  peculiar  smell  of  the 
pine  forests,  but  another  part  attracts  oxygen  from  the 
air,  and  is  converted  into  resin  (§  556). 

Resinous  juices,  which  harden  in  the  air,  forming 
solid  resins,  exude,  either  spontaneously  or  through  in- 
cisions made  for  the  purpose,  not  only  from  our  fir- 
trees,  but  also  from  many  other  trees  and  shrubs,  partic- 
ularly those  of  hot  climates.  Almost  all  the  resins  oc- 
curring in  commerce  are  procured  in  this  manner. 
Experiment.  —  Resin  is  deposited  most  abundantly 
in  those  parts  of  the  trees  where 
the  branches  join  the  trunk;  wood 
impregnated  with  such  resin  is 
called  resinous  wood.  If  a  piece  of 
resinous  wood  is  lighted  at  the 
upper  end,  and  held  by  a  wire  in 
an  oblique  position  over  a  basin  of 
water,  one  portion  of  the  resin  burns 
up  with  a  sooty  flame,  while  an- 
other part  is  melted  by  the  heat,  and 
runs  down  into  the  vessel  beneath.  Resin  is  not  sol- 
uble in  water;  hence  it  hardens  in  the  latter  without 
mixing  with  it.  In  this  manner  —  by  roasting —  resins 
may  be  prepared  from  many  plants  ;  but  the  color  of 
the  resins  thus  prepared  is  usually  dark,  because  some 
of  the  resin  has  become  burnt,  and  is  thereby  richer  in 
carbon,  according  to  the  general  law,  that  hydrogen  is 
always  burnt  before  carbon. 

Experiment.  —  Pour  strong  alcohol  upon   some  res- 
inous wood,  and  let  it  remain  for  a  day  in  a  warm 
place;   the  resin  is  dissolved,  and  the  woody  fibre  re- 
mains behind.     The  solution  is  poured  into  eight  timea 
48* 


570 


VEGETABLE    MATTER. 


its  quantity  of  water,  which  is  thereby  rendered  milky, 
because  the  resin  is  precipitated,  but  in  such  a  state  of 
fine  division  that  it  floats  about  in  the  water  in  the 
form  of  small  globules.  If  this  milky  fluid  is  heated  to 
the  boiling  point,  the  resinous  particles  soften  and  unite 
with  each  other  in  small  lumps,  which  may  be  taken 
out  and  pressed  together  in  larger  masses.  This  is  a 
third  method  of  extracting  resin  from  vegetable  sub- 
stances. 

DIFFERENT   SORTS  OF  RESIN. 

570.  The  following  are  the  most  important  resins :  — 

Pine-resin  is  the  resin  of  our  pine-trees. 

Galipot  is  a  very  clear  yellowish-white  kind  of  pine- 
resin,  imported  from  France. 

Copal  is  of  a  yellowish-white  color,  turning  to  brown, 
and  very  hard ;  it  comes  to  us  covered  with  sand  and 
earth,  from  which  it  is  freed  by  washing  it  with  lye  and 
by  scraping.  The  copal  of  the  West  Indies  and  Africa 
has  a  smooth  surface,  but  that  of  the  East  Indies  is 
wrinkled  and  uneven.  It  is  insoluble  in  common  alco- 
hol, but  it  partly  dissolves  in  absolute  alcohol,  and  dis- 
solves entirely  in  ether ;  the  East  India  copal  dissolves 
the  most  readily. 

Dammar  a  resin  (Kauri  or  Cowdee)  is  colorless  or 
yellowish,  tolerably  hard ;  comes  from  the  East  Indies. 

Mastic  is  yellowish,  transparent,  comes  in  rounded 
tears,  and  exudes  from  a  species  of  Pistacia,  a  tree 
growing  principally  in  Greece. 

Sandarach,  much  resembling  mastic,  but  yet  more 
Brittle,  is  the  product  of  an  evergreen  tree  which  grows 
in  Africa. 

Lac  exudes  from  several  species  of  Ficus  growing  in 
the  East  Indies,  through  punctures  made  by  a  small 
insect  called  the  Coccus  lacca. 


RESINS     AXD    GlT.M-RKSlNS. 

a.)  Stick-lac  is  the  name  given  to  the  juice  dried 
npon  the  twigs. 

b.)    Seed-lac,  when  it  is  broken  off  from  the  twigs. 

c.)  Shellac,  when  it  is  melted  and  strained  through  a 
cloth  to  remove,  impurities.  The  liquefied  resin  is  com- 
monly made  to  drop  upon  large  leaves,  and  cooled .  it 
thus  spreads  out  into  thin  plates.  The  finest  shellac 
has  an  orange  color,  that  of  inferior  quality  a  dark- 
brown  color.  It  is  very  hard  and  tenacious,  and  for 
this  reason  is  generally  used  in  the  manufacture  of 
sealing-wax. 

Benzoin  flows  from  incisions  made  in  a  tree  of  the 
East  Indies.  The  resin  exuding  during  the  first  three 
years  forms  milk-white  grains,  but  that  formed  after- 
wards is  yellow  or  brown.  Both  sorts  are  kneaded  to- 
gether ;  hence  the  amygdaline  appearance  of  the  com- 
mon benzoin.  Its  agreeable  odor,  somewhat  like  that 
of  vanilla,  has  rendered  it  a  popular  ingredient  in  fu- 
migating pastilles,  and  also  in  fcosmetic  lotions  for 
beautifying  the  skin.  One  sixth  of  it  consists  of  ben- 
zoic  acid. 

Dragorf s-blood  is  a  brownish-red  colored  resin  ;  it  is 
the  produce  of  several  palm-trees  growing  in  the  East 
Indies. 

Guaiacwn,  a  brownish-green  resin,  and  also  an  olive- 
colored  variety  of  the  same,  are  obtained  by  roasting 
guaiacum-wood,  and  are  considerably  used  in  medicine. 

Resin  of  jalap  is  extracted  by  alcohol  from  the  roct 
of  the  jalapa. 

Many  other  resins  are  used  in  pharmacy,  for  in- 
stance, anime,  tacamahac,  elemi,  &c. 

*)71.  Bitumen.  —  Two  other  resins,  amber  and  aa- 
pnaltum,  which  are  obtained  from  the  earth  or  firom 
the  sea,  remain  to  be  mentioned. 


57*3  VEGETABLE    MATTER. 

Amber  probably  proceeds  from  the  forests  of  a  pri- 
meval age,  which  have  been  submerged  by  floods  of 
water.  The  resins  form  an  exception  to  the  general 
rule,  —  they  do  not  putrefy  or  decay,  like  other  organic 
bodies.  The  amber-resin  might  accordingly  remain 
for  centuries  unchanged  in  the  earth,  or  in  the  sea, 
while  the  trees  from  which  it  exuded  were  changed  into 
mould  and  earth,  or,  chemically  speaking,  became  de- 
composed into  carbonic  acid,  water,  &c.  Amber  is 
found  most  frequently  in  the  Baltic  and  on  its  coasts, 
and  in  many  brown-coal  mines.  Its  hardness  and  te- 
nacity are  well  known,  since  it  is  formed  into  various 
articles  which  are  usually  manufactured  from  glass  or 
horn.  It  differs  from  other  resins,  as  it  yields  on  fusion 
succinic  acid,  and  undergoes  a  change,  in  consequence 
of  which  it  then  becomes  soluble  in  alcohol  and  oils, 
which  scarcely  attack  it  in  its  unmelted  state.  By 
longer  fusion  it  becomes  black,  and  is  then  called 
amber-colophany ;  it*  yields,  at  the  same  time,  a  very 
disagreeably  smelling  empyreumatic  oil,  oil  of  amber, 
which  is  sometimes  used  in  medicine. 

Asphaltum,  or  pitch  of  Judea,  is  likewise  a  mineral 
resin,  which  is  found  in  many  of  the  seas  of  Asia,  par- 
ticularly in  the  Dead  Sea.  It  has  a  black  color,  and 
great  similarity  to  the  black  resin  which  is  obtained 
by  the  evaporation  of  pit-coal  tar  (factitious  asphal- 
tum).  Asphaltum  is  found  in  other  places,  and  has 
a  soft  consistency,  and  resembles  turpentine  (Barbadoes 
tar)  ;  this  kind  has  in  later  times  been  mixed  with 
sand  and  lime  for  making  artificial  pavements  and 
tiles.  It  is  very  probable  that  these  two  resins,  as  also 
petroleum,  are  derived  from  layers  of  pit-coal  which 
have  been  heated  in  the  interior  of  the  earth  by  vol- 
carvic  fires. 


RESINS    AND    GUM-RESINS.  573 

572.  Similar  resinous  substances,  of  a  black  color  and 
disagreeable  odor,  are  also  artificially  formed  whenever 
animal  and  vegetable  substances  are  heated  with  an 
insufficient  supply  of  air,  especially  during  dry  distil- 
lation of  the  same.     When  in  a  fluid  form  thev  are 
called  tar ;  in  a  solid  form,  black  pitch. 

PROPERTIES  OF  RESIN. 

573.  It  was   stated  when  speaking  of  amber,  that 
resins  are  substances  which  do  not  undergo  decay ;  in- 
deed, they  have  the  power  to  protect  from  decomposi- 
tion other  bodies  which  very  readily  pass  into  decay 
or  putrefaction,  —  for  instance,  flesh.     On  this  account 
they  were  formerly  used  for  embalming  dead  bodies, 
which  are  now  found,  after  the  lapse  of  centuries,  dried 
to  mummies,  in  the  pyramids  of  Egypt. 

574.  Resin  and  Water.  —  The  resins  as  a  general  rule 
are  insoluble  in  water,  and  therefore  tasteless  ;  but  some 
of  them  in  very  small  quantities  may  be  dissolved,  and 
these  usually  have  a  bitter  taste.     But  many  of  the  res- 
ins which  occur  in  commerce  contain  some  water  in  a 
state  of  minute  division,  and  are  thereby  rendered  dull 
and  opaque ;  common  pine-resin  and  boiled  turpentine 
furnish  examples  of  this. 

Colophony  or  Rosin.  —  Ex- 

Fig.  213.  .  TT  f 

penment.  —  Heat  a  piece  of 
the  solid  turpentine  (§  551), 
or  else  some  pine-resin,  in  a 
spoon,  till  all  the  water  is 
evaporated ;  the  anhydrous  res- 
in will  now  appear  perfectly 
transparent.  In  this  state  it 
is  called  colophony,  or  rosin. 


VEGETABLE  MATTER. 

being  white  when  it  is  moderately  heated,  but  brown 
when  the  heat  is  so  strong  as  to  convert  a  part  of  the 
resin  into  black  pitch.  Colophony  is  so  brittle,  that  it 
may  easily  be  reduced  to  a  powder.  When  the  bow  of 
a  violin  is  rubbed  with  it,  the  rosin  powder  formed  re- 
mains adhering  to  the  fibres,  and  these  then  again  ad- 
here better  to  the  strings  of  the  violin.  A  similar  effect 
is  produced  on  the  cords  which  sustain  the  weights  in 
clocks  when  they  are  rubbed  with  rosin  to  prevent  their 
slipping.  The  resins,  accordingly,  exert  an  effect  con- 
trary to  that  of  oil ;  by  resin,  a  rough,  uneven  surface  is 
produced,  by  oil,  a  smooth,  slippery  surface. 

575.  Action  of  Heat  on  Resins. —  The  experiment  first 
performed  reveals  at  the  same  time  another  property  of 
resin,  namely,  its  easy  fusibility.  Most  of  the  resins 
require,  in  order  to  become  fluid,  a  heat  which  is  some- 
what higher  than  that  of  boiling  water.  If  the  melted 
rosin  is  poured  upon  a  board,  it  spreads,  and  forms 
after  ^hardening  a  solid,  brilliant  coating  on  the  wood. 
The  resins  are  hereby  well  adapted  for  protecting  wood 
or  metal  from  the  penetration  of  air  or  water.  For  this 
reason,  iron  rails  and  iron  ornaments  are  covered  with  a 
coating  of  pitch,  to  prevent  them  from  being  so  quickly 
oxidized  by  the  oxygen  of  the  air ;  for  the  same  reason, 
also,  wine-casks  and  beer-barrels  are  smeared  with  pitch, 
that  no  air  may  penetrate  into  the  casks,  and  that  no 
beer  may  penetrate  into  the  staves.  The  wood-work  of 
ships,  the  hatches,  &c.,  are  covered  with  tar  to  keep  out 
the  sea-water  and  rain  ;  and  finally,  also,  the  solid  and 
tenacious  resin,  shellac,  is  employed  in  the  form  of 
sealing-wax  as  a  protection  against  curiosity. 

Sealing-wax.  —  Experiment.  —  Melt  together  in  a 
small  ladle  one  fourth  of  an  ounce  of  pale  shellac,  one 
dram  of  turpentine,  one  dram  of  cinnabar,  and  three 


RESINS    AND    GUM-RESINS.  575 

fourths  of  a  dram  of  prepared  chalk ;  scrape  out  the 
mass  while  yet  ductile,  and  roll  it  out  into  sticks  by 
the  hands,  moistened  with  water.  The  turpentine  ren- 
ders the  sealing-wax  more  inflammable,  and  the  cinna- 
bar imparts  to  it  the  favorite  red  color.  Various  other 
colors  are  given  to  it  by  chrome-yellow,  azure-blue, 
mountain-green,  lamp-black,  bronze-powder,  &c. 

576.  Rosin-gas.  —  Experiment.  —  When  rosin  is  heat- 
ed above  its  melting  point,  it  kindles  and  burns  with 
a  luAjaous  and  sooty  flame,  leaving  behind  some  char- 
coal, ^therefore  powdered  rosin,  when  blown  into  the 
flame  of  a  lamp,  burns  vividly.     In  many  places  illu- 
minating' gas  is  prepared  from  it,  by  letting  it  drop  in  a 
melted  state  upon  coke,  which  is  heated  to  redness  in 
an  iron  cylinder  (rosin-gas). 

Burnt  Pitch.  —  If  the  rosin,  after  it  has  burnt  for  some 
time,  is  extinguished  by  putting  a  board  over  it,  we 
shall  have  as  a  residuum  a  black,  burnt  resin,  ship-pitch, 
and  shoemaker's  wax-)  possessing  great  tenacity.  . 

Lamp-black.  —  Experiment.  —  If  you  hold  a  cone 
made  of  blotting-paper  over  burning  pine-wood,  it  will 
soon  become  lined  with  soot.  The  well  known  lamp- 
black is  prepared  on  a  large  scale  by  a  similar  method. 
Resinous  wood,  or  the  resin  itself,  is  burnt  with  an  in- 
sufficient supply  of  air  in  a  stove  furnished  with  long 
flues,  or  with  a  chamber  in  which  the  smoke  deposits 
its  carbon  on  its  passage  through. 

Experiment.  —  If  some  amber  is  scattered  on  glow- 
ing charcoal,  a  vapor  having  a  pleasant  balsamic  odor 
is  emitted  from  it  as  it  smoulders  away.  Amber, 
frankincense,  benzoin,  and  mastic  are  on  this  account 
frequently  used  for  fumigating  purposes. 

577.  Electrophorus.  —  Experiment. —  Rub  a  stick  of 
sealing-wax   for  some  minutes  upon  a  piece  of  cloth, 


570  VEGETABLE    MATTER. 

and  then  approach  it  to  some  small  shreds  of  blotting- 
paper  ;  they  will  fly  up  to  the  sealing-wax,  and  remain 
adhering  to  it  for  some  time.  This  attraction  is  effected 
by  electricity  (resinous  or  negative  electricity),  which  is^ 
generated  in  the  resins  by  friction.  If  you  pour  a  mix- 
ture of  shellac  and  rosin  into  a  tin  plate  in  order  to 
obtain  a  larger  surface,  you  will  be  enabled  to  extract 
the  electricity  from  it  in  the  form  of  sparks,  and  to  col- 
lect it ;  this  is  called  an  electrophorus  (bearer  of  electri- 
city). This  mysterious  power  has  received  the  name 
of  electricity  from  fj\€Krpov,  the  Greek  word  for  am- 
ber, in  which  the  electrical  phenomena  were  first  ob- 
served. 

578.  Resin  and  Alcohol.  —  Experiment.  —  Wrap  half 
an  ounce  of  sandarach  in  paper,  and  break  it  with  a 
hammer  into  smaller  pieces ;  then  mix  it  with  an  eighth 
of  an  ounce  of  sand,  which  has  been  previously  freed 
from  its  pulverulent  particles  by  washing,  and  after- 
ward^ thoroughly  dried,  and  pour  the  mixture  into  a 
glass  vessel,  with  two  ounces  of  strong  alcohol.  Tie 
a  piece  of  bladder  over  the  vessel,  and  let  it  remain 
for  several  days  in  a  warm  place,  frequently  stirring  it 
round.  The  clear  solution  of  resin  thus  obtained  is 
called  lac-varnish,  because,  when  smeared  over  metal, 
wood,  or  paper,  it  leaves  behind,  after  the  alcohol  has 
evaporated,  a  varnished,  shining  coat.  If  alcohol  is 
poured  upon  the  sandarach,  unmixed  with  sand,  the 
resinous  powder  will  cake  together  on  the  bottom  of 
the  vessel,  forming  a  tenacious  mass  of  resin,  which 
dissolves  much  more  slowly.  To  varnish,  then,  is  to 
smear  the  surface  of  any  thing  with  resin.  By  this 
coat  of  varnish  articles  not  only  acquire  a  beautiful  bril- 
liancy, but  are  rendered  at  the  same  time  impervious 
to  air  and  water.  When  paper  articles  —  for  instance, 


GUMS    AND    GUM-RESINS. 


57V 


drawings,  charts,  &c.  —  are  to  receive  a  coat  of  varnish, 
glue^or  a  solution  of  gum  must  previously  be  spread 
over  them  several  times,  as  the  solution  of  resin  would 
otherwise  penetrate  into  the  fibres  of  the  paper,  and 
render  it  gray  and  transparent.  This  imbibition  is 
usually  prevented  in  wooden  articles  by  smearing  them 
with  linseed  oil  before  putting  on  the  varnish.  When 
the  varnish  is  applied  on  places"  that  are  wet,  white 
opaque  spots  are  formed,  because  the  resin  is  separated 
by  the  water  as  a  dull  white  powder. 

Experiment.  —  Dissolve  half  an  ounce  of  shellac  in 
strong  alcohol ;  a  turbid  liquid  is  obtained,  as  the  shel- 
lac contains,  besides  the  resin,  small  quantities  of  wax 
and  mucilaginous  substances,  which  float  about  undis- 
solved  in  the  solution  of  resin.  This  solution  is  also 
employed  as  a  lac  varnish,  but  much  more  frequently 
as  the  so-called  polish  of  the  cabinet-makers  ;  that  is,  as 
a  solution  of  resin,  which  they  rub  continuously  upon 
the  wood  with  a  ball  of  linen,  until  the  alcohol  has 
evaporated.  By  this  means  a  yet  smoother  and  finer 
polish  is  obtained  than  by  merely  applying  the  resinous 
solution  with  a  brush,  the  marks  of  which  frequently 
remain  visible.  The  finer  articles  of  furniture  are 
usually  polished,  the  more  ordinary  ones  varnished. 

579.  Resins  and  Oils.  —  Experiment.  —  Mix  half  an 
ounce  of  dammara  resin  with  some  sand,  and  pour  over 
the  mixture  two  ounces  of  oil  of  turpentine ;  after  a  few 
days  you  will  obtain  an  almost  complete  solution,  as 
the  volatile  oils  are  likewise  able  to  dissolve  resins. 
These  solutions  are  also  frequently  employed  as  lac 
varnishes;  they  dry, •indeed,  more  slowly,  but  form 
a  more  tenacious  coating,  which  is  less  liable  to  crack. 
The  paler  and  finer  varieties  of  varnish  are  principally 
prepared  from  amber,  copal,  dammara,  shellac,  sanda- 
49 


578  VEGETABLE     MATTER. 

rach,  and  mastic ;  the  inferior  and  darker  kinds,  from 
amber-colophony,  common  colophony,  turpentine,  as- 
phaltum,  &c.  A  yellow  color  is  sometimes  given  to 
the  pale  varnishes  by  the  addition  of  dragon's-blood,  or 
gamboge. 

The  resins  are  likewise  soluble  in  fat  oils.  Many 
ointments  and  plasters  of  the  apothecaries  consist  of 
mixtures  of  fats  and  resins,  and  it  is  the  latter  which 
communicate  to  the  former  the  property  of  adhering  to 
the  skin.  Turpentine  is  usually  employed  for  this  pur- 
pose. 

580.  Resinous  Soap.  —  Experiment.  —  Boil  in  a  jug  a 
quarter  of  an  ounce  of  rosin,  with  one  ounce  of  strong 
potassa  or  soda  lye,  and  then  gradually  add  lye  by 
spoonfuls,  until  a  sample  of  the  mixture  dissolves  in  hot 
water,  forming  a  clear  liquid.  The  mass  hardens,  on 
cooling,  into  a  solid  soap  (a  compound  of  the  resinous 
acid  and  potassa,  or  soda).  The  resins,  as  we  see 
comport  themselves  towards  strong  bases  like  the  fat 
acids,  and  hence  have  an  extensive  application  in  the 
manufacture  of  soap,  being  mixed  with  the  fats  in  dif- 
ferent proportions  in  the  manufacture  of  the  cheaper 
kinds  of  soap. 

Experiment.  —  Mix  a  solution  of  resin  soap  with  a 
solution  of  alum  ;  an  insoluble  combination  of  resinous 
acid  and  alumina  is  formed.  Resin  soap  is  employed 
for  the  sizing  of  paper ;  it  is  first  introduced  into  the 
vat  containing  the  pulpy  mass  of  which  the  paper  is 
to  be  made,  and  then  the  solution  of  alum  is  added. 
There  is  thus  formed  round  each  fibre  of  the  paper  a 
thin  layer  of  insoluble  alumina  soap  (resinous  acid  and 
alumina),  which  prevents  the  spreading  of  the  ink. 
According  to  the  old  method,  the  sheets  of  paper  were 
passed  through  a  solution  of  glue,  whereby  only  a  thin 


GUMS    AND    GUM-RESINS. 

layer  of  glue  was  formed  on  the  surface  of  the  paper. 
This,  kind  of  paper  allows  the  ink  to  spread,  when  the 
coat  of  glue  has  been  scraped  off  by  erasure ;  but  this 
may  be  prevented  by  rubbing  some  resin  —  sandarach 
is  the  best  —  upon  the  spots  erased. 

Resins  combine  with  bases,  and  their  solutions  red- 
den Jitmus-paper.  Accordingly,  they  may  be  regarded 
as  acids. 

581.  Composition  of  the  Resins.  •*—  By  alternate  treat 
ment  of  the  resins  with  cold  or  hot,  weak  or  strong  al 
cohol,  or  with  ether,  various  kinds  of  resin  may  be  ex- 
tracted from  most  of  them,  which  have  been  designated 
by  the  terms  alpha  (a),  beta  (/3),  or  gamma  (y)  resins. 
The  natural  resins  are  accordingly  to  be  regarded  as 
mixtures  of  several  simple  resins. 

Only  the  three  elements  carbon,  hydrogen,  and  oxy- 
gen (C,  H,  O)  occur  in  the  resins.  That  they  contain 
somewhat  more  oxygen,  and  less  hydrogen,  than  the 
volatile  oils,  has  already  been  stated  (§  566)  ;  but,  never- 
theless, they  belong  to  the  bodies  rich  in  hydrogen,  since 
they  burn  with  a  strong  flame. 

GUM-RESINS. 

582.  If  you  divide  a  stem  of  poppy,  lettuce,  or  celan- 
dine, a  white  or  yellow  juice  exudes,  which  dries  up  in 
the  air  or  by  the  heat  of  the  sun,  forming  a  yellow  or 
brown  amorphous  mass.     This  rnilky  juice  consists  of 
a  solution  of  gum,  intimately  mixed  with  minute  drops 
of  resin ;  thus  it  forms  a  natural  emulsion.     This  kind 
of  dried,  half-resinous,    half-gummy  vegetable  juice  is 
called,  from  these  two  proximate  constituents,  gum-resin. 
Many  plants  of  hot  climates  are  especially  rich  in  such 
resins,  and  from  them  are  principally  obtained  the  gum- 


580  VEGETABLE    MATTER. 

resins  occurring  in  commerce,  which  have  various  ap- 
plications, particularly  in  pharmacy.  Among  the  most 
important  are,  — 

Ammoniac  (gum  ammoniac),  the  inspissated  milky 
juice  of  an  African  umbelliferous  plant ;  it  has  a  yel- 
lowish or  brown  color,  and  a  strong,  peculiar  smell  and 
taste. 

Assaf&tida  (stercus  diaboli),  the  juice  of  a  Persian 
umbelliferous  plant,  having  a  very  unpleasant  smell, 
like  that  of  garlic ;  it  has  a  milk-white  appearance 
when  freshly  broken,  but  quickly  changes  in  the  air  and 
light  into  a  pink  color. 

Aloes,  which  has  a  brown  or  black  color,  and  is  ex- 
ceedingly bitter ;  it  is  the  dried  juice  of  the  aloe-plant, 
which  grows  in  great  abundance  on  the  Cape  of  Good 
Hope  and  the  adjacent  islands. 

Euphorbium,  which  comes  in  brownish-yellow  tears 
from  the  African  plant  Euphorbia  Canariensis,  and  con- 
tains a  very  acrid  substance,  in  consequence  of  which 
it  vesicates  the  skin,  and,  when  snuffed,  excites  inflam- 
mation of  the  nostrils  and  the  most  violent  sneezing. 

Galbanum,  a  yellowish  or  brownish  substance,  having 
a  strong  and  peculiar  odor ;  it  is  obtained  from  an  ever- 
green plant  of  Persia. 

Gamboge,  which  occurs  in  orange-colored  masses  or 
sticks  ;  it  is  obtained  from  the  leaves  of  an  East  Indian 
plant,  and  is  principally  used  as  a  yellow  water-color  in 
painting. 

Myrrh;  the  better  sorts  occur  in  pale,  brownish-yellow 
fragments,  the  inferior  sorts  in  dark  brownish-red  pieces ; 
it  has  a  bitter  taste  and  a  balsamic  odor,  and  exudes 
from  incisions  made  in  a  tree  growing  in  Arabia. 

Frankincense  (olibanum),  which  comes  in  yellowish- 
white,  brittle,  roundish  fragments;  the  juice,  inspis- 


GUMS    AND    GUM-RESINS.  581 

Bated  in  the  air,  is  obtained  from  a  tree  in  Persia.  It 
yields  an  agreeable  odor  upon  glowing  coals,  and  hence 
is  much  used  for  fumigating  purposes. 

Opium,  a  milky  juice,  which  exudes  from  incisions 
macje  in  the  breads  of  unripe  poppies,  and  is  inspissated 
by  exposure  to  the  air;  it  occurs  in  large  lumps  of  a  dark 
brown  color,  having  a  bitter  taste  and  an  offensive  nar- 
cotic odor.  The  soporific  effects  of  it  are  well  known. 

Lactucarium,  of  a  brown  color,  and  having  somewhat 
the  odor  of  opium ;  it  is  the  inspissated  juice  of  several 
kinds  of  lettuce. 

Opoponax,  Sagapenum,  Scammony,  and  many  others. 

PROPERTIES  OF  THE    GUM-RESINS. 

583.  Experiment.  —  Triturate  some  one  of  the  gum- 
resins  with  water ;  the  gum  is  hereby  dissolved,  and  a 
turbid,  milky  liquid  (emulsion)  is  obtained.     If  this  is 
boiled  for  some  time,  the  softened  particles  of  resin  cake 
together,  and  separate  as  lumps ;  the  liquid,  having  be- 
come clear,  contains  now  only  the  gum  in  solution. 

Experiment.  —  If  strong  alcohol  is  poured  over  the 
gum-resins,  and  they  are  digested  together  for  some 
time,  the  resin  only  is  dissolved,  while  the  gum  remains 
undissolved.  The  well-known  tincture  of  myrrh  is  a 
solution  in  alcohol  of  the  resinous  particles  contained 
in  the  myrrh.  Most  of  the  gum-resins  contain,  besides 
resin  and  gum,  a  small  quantity  also  of  volatile  oils,  to 
which  they  owe  their  peculiar  odor. 

CAOUTCHOUC  (GUM  ELASTIC). 

584.  There  exudes  from  several  large  South  Amer- 
!can  trees,  when  incisions  are  made  in  them  through 

49* 


!=> 


582  VEGETABLE    MATTER. 

the  outer  and  inner  bark,  a  milky  juice,  which  dries  in 
the  air  into  a  white  elastic  mass,  quite  insoluble  in  wa- 
ter and  alcohol.  It  is  gum  elastic,  or  caoutchouc.  The 
drying  proceeds  more  rapidly  when  the  milky  juice  is 
spread  upon  moulds  of  clay  or  lime,  and  then  suspended 
over  a  fire.  If,  after  the  gum  is  dry,  the  clay  or  lime  is 
removed  by  washing,  hollow  articles  of  caoutchouc  are 
obtained,  but  which  have  a  black  or  sooty  appearance 
on  account  of  the  soot  mixed  with  them. 

Experiment.  —  Caoutchouc  at  the  ordinary  tempera 
ture  is  hard  and  stiff,  but  it  becomes  soft  when  it  is  put 
into  hot  water  or  in  a  warm  oven.     Cut  from  one  of 
these  caoutchouc  bottles,  softened 
by  heat,  a  square  piece,  apply  it 
evenly  round   the    ends   of    two 
glass  tubes,  and  then  clip  off  with 
a  pair  of  scissors  the  ends  of  the  strip  in  the  direction 
marked  out  in  the  annexed  figure:  the  fresh  surfaces 
of  the  caoutchouc  adhere  firmly  to  each  other  (but  still 
more  closely  when  they  are  pressed  together  with  the 
nail,  yet  without  touching  the  freshly  cut  surfaces),  and 
Fig  215  thus  is  formed  a  tube,  which,  firm- 

ly tied  at  both  ends,  binds  the 
two  glass  tubes  air-tight  with  each 
other.  In  this  manner,  the  glass 
tubes  occurring  in  chemical  apparatus  are  made  pliant 
and  flexible,  and  the  risk  of  breaking  them  is  thereby 
diminished. 

Experiment.  —  Pour  some  petroleum  upon  a  few 
pieces  of  caoutchouc ;  the  caoutchouc  will  swell  up  in 
it,  and  may  then  be  converted  into  a  homogeneous 
mass.  When  melted  with  shellac,  the  mass  affords  a 
very  permanent  cement  for  wood,  stone,  and  iron  (ship- 
glue). 


GUMS    AND    GUM-RESINS.  583 

Experiment.  —  If  ether,  oil  of  turpentine,  or  oil  of  pit- 
coal  tar  is  poured  upon  caoutchouc,  a  complete  solu- 
tion is  obtained.  Solutions  of  this  kind  are  now  fre- 
quently employed  for  rendering  fabrics  waterproof 
(Mackintosh).^  When  strongly  heated  with  alcohol, 
caoutchouc  forms  a  homogeneous,  tenacious,  black 
mass,  which  is  very  well  adapted  for  smearing  shoe- 
leather. 

Experiment.  —  When  caoutchouc  is  held  in  a  burn- 
ing lamp,  it  takes  fire  and  burns  with  a  vivid,  sooty 
flame,  like  petroleum  or  oil  of  turpentine,  and  melts 
into  a  black,  glutinous  residue.  This  melted  caout- 
chouc is  very  serviceable  for  preventing  the  sticking 
of  glass  stoppers  in  bottles,  in  which  lye,  &c.,  is  kept ; 
the  stoppers,  when  coated  with  it,  remain  lubricous  for 
a  long  time. 

Caoutchouc  acquires  an  extremely  high  degree  of 
elasticity  by  intimately  mixing  it  with  sulphur,  or  sul- 
phuret  of  arsenic  (vulcanized  caoutchouc). 

Caoutchouc  is  one  of  the  few  solid  bodies  which  con- 
tain no  oxygen;  it  consists  only  of  carbon  and  hydro- 
gen, so  that  it  may  be  regarded,  as  it  were,  as  con- 
densed petroleum,  or  as  condensed  illuminating-gas. 

Gutta  Percha.  —  Under  this  name,  within  a  short 
time,  a  substance  resembling  caoutchouc  has  occurred 
in  commerce,  which  is  procured  from  the  milky  juice  of 
several  East  Indian  trees;  it  has  the  advantage  over 
caoutchouc,  that  it  becomes  quite  soft  and  plastic  by 
moderate  heating,  but  hard  again  on  cooling,  and  has 
found  already  various  applications  in  the  arts. 


584  VEGETABLE    MATTER. 

RETROSPECT   OF   THE   FATS,   VOLATILE    OILS,  AND 

RESINS. 

1.  The  fats,  volatile  oils,  and  resins  are  among  the 
very   generally  diffused   substances   of    the   vegetable 
kingdom ;  most  of  them  comport  themselves  like  indif- 
ferent bodies,  many  like  feeble  acids. 

2.  As  occurring  in  nature,  they  are  mixtures  of  sev- 
eral similar  substances  with  each  other,  which  are,  — 

a.)  The  fats  ;  mixtures  of  solid  fats.(stearine,  marga- 
rine) and  of  fluid  fats  (oleine,  glycerine). 

b.)  The  volatile  oils ;  mixtures  of  solid  stearoptene 
and  fluid  oleoptene. 

c.)  The  resins ;  mixtures  of  several  different  kinds  of 
resin  (alpha,  beta,  gamma  resins,  &c.). 

3.  As   respects   their   elementary  constitution,   they 
consist  only  of  the  three  elementary  substances,  carbon, 
oxygen,  and  hydrogen ;  but  they  are  always  poor  in  ox- 
ygen and  rich  in  hydrogen.     ( Some  volatile  oils  contain 
no  oxygen.) 

4.  On  account  of  the  excess  of  hydrogen,  — 

a.)  They  burn,  when  ignited,  with  a  brisk  flame,  and 
yield,  on  decomposition  by  a  glowing  heat,  much  com- 
bustible gas. 

b.)  Most  of  them  are  so  light  that  they  float  upon 
water. 

c.)  They  are  dissolved  only  in  liquids  which  are  like- 
wise rich  in  hydrogen  and  poor  in  oxygen  ;  for  instance, 
in  alcohol  and  ether,  but  not  in  water. 

5.  They  are  either  liquid,  or  are  easily  rendered  so, 
even  when  gently  heated. 

6.  The  fats  of  animals  have  exactly  the  same  consti- 
tution as  the  vegetable  fats. 

7.  By  the  addition  of  oxygen  many  kinds  of  fat  be- 


EXTRACTIVE    MATTER.  585 

come  solid  and  hard  (varnish  oils),  others,  on  the  con- 
trary, become  rancid  without  hardening  (unctuous 
oils). 

8.  The  fats  are  resolved,  by  strong  inorganic  bases, 
into  peculiar  acids  insoluble  in  water  (fat  acids),  and 
into  an  organic  base  (oxide  of  glyceryle).     The  sepa- 
rated fat  acids  hereby  combine  chemically  with  the  in- 
organic bases,  forming  soaps.     The  alkalies  form,  with 
the  fat  acids,  soaps  which  are  soluble  in  water ;  the  ox- 
ides of  the  earths  and  metals,  on  the  contrary,  form 
soaps  which  are  insoluble  in  water. 

9.  The  volatile  oils,  by  the  addition  of  oxygen,  pass 
into  resins ;  often  also,  at  the  same  tifne,  into  acids. 

10.  The  resins  evince  no  great  affinity  for  oxygen ;  at 
least  they  do  not  alter,  however  long  they  may  be  ex- 
posed to  the  air. 

11.  Many  of  the  resins*  combine   with  the  alkalies, 
forming  soaps  soluble  in  water;  with  the  earths  and 
metallic  oxides,  forming  soaps  insoluble  in  water  (resin- 
ous soaps). 

12.  Balsams  are  mixtures  of  resins  with  volatile  oils 
gum-resins  are  mixtures  of  resins  with  gum. 


XII.    EXTRACTIVE   MATTER. 

• 
585.   Extracts.  —  The  vegetable  substances  hitherto 

considered  are,  if  we  except  the  volatile  oils  and  some 
resins,  mostly  without  taste  and  without  any  striking 
medicinal  effect ;  most  of  them  occur  very  generally  dif- 
fused in  the  vegetable  kingdom,  and  are  found  in  al- 
most all  vegetables.  But  we  observe  in  many  plants  a 
peculiar  taste,  and  when  swallowed  a  peculiar  effect 


586  VEGETABLE     MATTER. 

upon  our  bodies ;  consequently,  there  must  be  othei 
special  substances  present,  from  which  the  taste  and 
effect  proceed.  Wormwood  and  rhubarb  have  a  bit- 
ter taste,  pepper  and  henbane  a  pungent  and  sharp 
taste,  the  roots  of  couch-grass  and  of  liquorice  a  sweet 
taste.  *  When  introduced  into  the  stomach,  wormwood 
is  stomachic,  rhubarb  purgative,  pepper  stimulating, 
henbane  narcotic,  &c.  These  and  similar  actions  must, 
even  at  an  early  period,  have  excited  the  attention  of 
man,  and  led  him  to  extract  the  tasting  and  medicinal 
principles  from  the  plants,  and  to  use  them  in  med- 
icine. This  extraction  was  effected  in  a  simple  man- 
ner, from  the  jutey  parts  of  the  plants  by  expression ; 
from  the  drier  parts,  by  treating  them  with  cold  water 
(maceration),  or  with  hot  water  (infusion),  or  by  boil- 
ing them  with  water  (decoction).  As  the  vegetable 
juices  or  extracts  would  soori  become  sour  or  mouldy, 
the  water  is  evaporated  away ;  by  this  means,  a  pulpy 
or  pasty  mass,  or,  on  more  complete  desiccation,  a  solid 
amorphous  mass,  is  obtained,  which  is  called  an  extract 
(watery  extracts),  and  may  be  kept  for  years  unchanged 
and  undecomposed.  Sometimes,  instead  of  water,  al- 
cohol or  ether  is  used  as  a  solvent  (alcoholic  and  ethe- 
real extracts).  Many  of  these  extracts  are  always  kept 
on  hand  by  the  apothecaries  as  medicines,  and  one 
ounce  of  them  frequently  contains  as  much  active 
matter  as  one  pound,  or  even  several  pounds,  of  the 
vegetable  substance  from  which  they  were  prepared. 

It  has  already  been  stated,  that  most  of  the  vegetable 
juices  contain  sometimes  larger,  sometimes  smaller, 
quantities  of  starch  (sediment),  mucus,  gum,  sugar, 
tannin,  chlorophyll,  vegetable  albumen,  salts,  acids, 
&c. ;  hence,  all  these  substances  do  not  -volatilize  on 
evaporation,  but  some  of  them  must  also  be  present  in 


EXTRACTIVE    MATTER. 


587 


the  \vatery  extracts.  It  is  likewise  clear,  that  in  the 
spirituous  and  ethereal  extracts  all  those  substances 
which  can  be  dissolved  from  the  vegetable  substances 
acted  upon  by  either  alcohol  or  ether  must  be  present , 
for  example,  resins,  fats,  &c.  The  extracts  may,  &•- 
cordingly,  be  *  regarded  as  mixtures  of  various  kinds  of 
vegetable  matter,  as  mixtures  of  known  with  unknown 
vegetable  matter,  of  that  having  taste  with  that  having 
.no  taste,  of  the  active  with  the  inert,  of  the  colorless 
with  the  colored,  &c. 

586.  Extractive  Matter.  —  On  closer  examination  of 
the  vegetable  juices  or  extracts,  it  has  been  found  that 
after  the  known  substances,  such  as  starch,  sugar,  albu- 
men, &c.,  have  been  removed  from  them,  a  brown  or 
black  uncrystallizable,   soluble   mass   remains   behind, 
which  generally  possesses  in  a  greater  degree  the  taste 
and  the  medicinal  effect  of  the  plant  from  which  it  has 
been  extracted.     This  mass  is  called  extractive  matter, 
and  is  distinguished  by  the  following  and  other  prop- 
erties :  —  bitter  (in  wormwood,  buckbean,  aloes,   colo- 
cynth,  &c.),  aromatic  bitter  (in  the  root  of  the  sweet- 
flag,  in  hops,  &c.),  acrid  (in  senega-root,  soapwort,  &c.), 
siveet  (in  liquorice-root,  root  of  couch-grass,  &c.),  nar- 
cotic (in  hemlock,  henbane,  &c.).     The  name  was  ob- 
viously a  very  convenient  one,  since  it  applied  to  all 
the  innumerable  vegetable  substances  not  thoroughly 
examined,  which  possessed  a  dark  color  and  did  not 
crystallize,  however  different  might  be  their  chemical 
constitution.     How  great  this  difference  may  be  we  in- 
fer from  this,  that  most  vegetable  substances,  for  in- 
stance, sugar  and  gum,  when  they  are  boiled  for  a  long 
time,  or  merely  exposed  to  the  air,  are  converted  into 
brown,  uncrystallizable  compounds. 

587.  The  reason  why  all  extracts  have  a  brown  or  a 


f»88  VEGETABLE    MATTER. 

black  color  is  to  be  sought  for  in  this  ready  changeable- 
ness  of  vegetable  matter. 

Experiment.  —  Pour  upon  some  ounces  of  sliced 
liquorice-root  six  times  the  quantity  of  boiling  water, 
and,  after  it  has  stood  for  some  days,  express  the  liquid ; 
when  this  has  been  filtered  through  blotting-paper,  it  is 
ctear,  transparent,  and  of  a  sherry- wine  color.  Upon 
evaporation,  we  obtain  from  it  a  black  extract,  the  well- 
known  Spanish  liquorice,  which,  when  redissolved  in 
water,  no  longer  yields  a  yellowish,  but  a  dark-brown 
liquid.  Not  only  the  color,  but  the  taste  also,  has  per- 
ceptibly changed.  Both  changes  clearly  show,  that 
during  the  evaporation  a  chemical  decomposition  of 
the  dissolved  matter  has  taken  place.  It  is  very  simi- 
lar to  that  which  happens  during  the  putrefaction  or 
slow  oxidation  of  wood ;  namely,  oxygen  is  absorbed 
from  the  air,  and  some  hydrogen  and  carbon  are  hereby 
oxidized  into  water  and  carbonic  acid,  whereby  sub- 
stances similar  to  humus,  richer  in  carbon,  and  con- 
sequently darker-colored,  are  formed.  These  are  in 
part  dissolved  in  the  water,  and  cause  the  dark  color  of 
the  liquid ;  but  they  are  in  part  no  longer  soluble,  and 
therefore  separate  from  the  solution  as  a  dark-colored 
sediment.  This  sediment  has  been  designated  by  the 
likewise  very  indefinite  term,  oxidized  extractive  matter. 
From  this  it  results  as  a  general  rule  in  the  preparation 
of  extracts,  that  the  evaporation  of  the  vegetable  juices 
should  be  conducted,  if  possible,  with  exclusion  of  air, 
and  at  a  gentle  heat ;  it  is  best  done  over  the  water- 
bath. 

588.  Cry  stalliz  able  Extractive  Matter.  —  In  modern 
times,  several  of  these  peculiar  substances  have  been  ob- 
tained in  a  crystalline  form,  consequently  as  fixed  and 
independent  compounds.  Many  of  these  behave  very 


EXTRACTIVE    MATTER.  589 

much  like  the  inorganic  bases  (potassa,  soda,  ammonia, 
&c.) ;  that  is,  they  are  able  to  neutralize  acids  and  to 
iorm  salts  with  them :  these  are  the  organic  bases 
(§  596).  Others,  on  the  contrary,  possess  neither  basic 
nor  acid  properties,  —  they  are  indifferent,  and  may  be 
called  crystailizable  extractive  substances,  at  least  until 
their  chemical  behaviour  shall  have  been  more  accu- 
rately ascertained  by  further  investigations.  As  yet, 
too  little  is  known  about  them  to  enable  us  to  express 
any  decided  opinion  concerning  them.  The  number  of 
the  plants  now  known  exceeds  a  hundred  thousand,  and 
it  is  not  improbable  that  extractive  matter  is  to  be 
found  in  most  of  them  ;  consequently  they  present  a 
fine  field  for  new  discoveries.  After  what  has  been  said, 
we  may  include  under  the  term  extractive  matter  all 
sorts  of  chemical  substances  of  indifferent  crystalliza- 
ble, and  of  indifferent  brown,  uncrystallizable  matter,  to 
which  in  most  cases  we  ascribe  the  peculiar  taste  and 
the  peculiar  medicinal  effects  of  plants.  Most  of  them 
are  -characterized  by  a  bitter  taste,  and  hence  are  fre- 
quently called  bitter  substances.  Some  of  them,  name- 
ly, those  which  are  insoluble  in  water,-do  not  evince  the 
taste  peculiar  to  them  until  they  are  dissolved  in  some 
other  liquid,  for  instance,  in  alcohol  or  ether. 

589.  The  best  known  of  these  peculiar  substances  will 
now  be  briefly  referred  to.  Their  names  (as  also  the 
names  of  coloring  matters  and  of  the  organic  bases)  are 
usually  formed  from  the  Latin  names  of  the  plants, 
with  the  addition  of  the  affix  in  or  ine. 

Absinthine,  from  wormwood,  very  bitter ;  a  colorless 
crystalline  mass. 

Amygdaline,  from  the  bitter  almonds,  slightly  bitter, 
crystallizes  in  lustrous  silky  scales ;  it  has  the  very  re- 
markable property  of  being  converted  into  a  volatile  oil 
50 


590  VEGETABLE  MATTER. 

containing  prussic  acid  (oil  of  bitter  almonds)  when  it 
is  ftiixed  with  dissolved  vegetable  albumen. 

Centaurine,  from  the  Chironia  centaurium,  bitter ;  as 
yet  only  known  as  an  extract. 

Cctrarine,  from  Iceland  moss,  bitter ;  a  white  powder. 

Columbine,  from  columbo-root,  very  bitter,  crystallizes 
in  white  prisms. 

Gentianine,  from  gentian-root,  very  bitter,  crystallizes 
in  yellow  needles. 

Imperatorine,  from  masterwort,  very  acrid  and  burn- 
ing; in  white  crystals. 

Lupuline,  from  hops,  an  agreeable  bitter ;  a  white  or 
yellowish  powder. 

Meconine^  from  opium  (poppy-juice),  acrid  to  the 
taste  ;  in  whi-te  crystals. 

Picrotoxine,  from  the  seeds  of  the  Cocculus  Indicus, 
very  bitter,  narcotic,  and  poisonous ;  in  white  needles. 

Quassine^  from  the  wood  of  the  quassia,  very  bitter ; 
in  white  crystals. 

Santonine,  from  worm-seed,  bitter,  in  white  crystals. 

Scillitinej  from  squill,  nauseously  bitter;  a  white 
amorphous  mass. 

Senegine^  from  senega-root,  acrid  and  astringent;  a 
white  powder. 

Glycyrrhizine.)  from  liquorice-root,  very  sweet ;  a 
pale-brown  amorphous  mass. 

Populine,  from  the  leaves  and  bark  of  the  poplar, 
sweet;  crystallizable  in  white  needles. 


Asparagine,  from  asparagus,  having  an  insipid  taste ; 
in  white  crystals. 

Smilacine,  from  the  root  of  the  sarsaparilla,  tasteless , 
in  white  crystals. 


COLORING    MATTER.  591 

By  far  the  greater  proportion  of  these  substances  con- 
sist of  the  three  elements  carbon,  hydrogen,  and  oxygen ; 
some  few  only  contain  also  a  little  nitrogen. 


XIII.     COLORING   MATTER,    OR   DYES. 

590.  WHEN  the  peculiar  substances  which  have  been 
treated  of  in  the  previous  section,  under  the  name  of  ex- 
tractive matters,  are  themselves  colored,  or  become  so  by 
the  action  of  other  substances,  they  are  called  coloring1 
matter,  or  dyes.  Most  of  those  colors  whose  inim- 
itable splendor  and  variety  we  admire  in  the  flowers  of 
plants  are  so  exceedingly  evanescent,  that  they  fade 
or  disappear  on  withering  or  drying,  and  very  rapidly, 
especially  when  they  are  exposed  at  the  same  time  to 
the  sunshine.  The  same  happens  when  we  attempt  to 
extract  or  separate  the  coloring  matter  by  expression,  or 
in  some  other  way.  A  few  plants  only  contain,  some- 
times in  the  roots  or  the  wood,  sometimes  in  the  leaves 
or  fruit,  coloring  juices  of  such  permanency  that  they 
are  more  difficultly  and  slowly  decomposed  by  the 
light ;  these  may  be  extracted,  and  then  employed  for 
coloring  other  substances.  These  colors,  however,  are 
turned  white  by  chlorine  or  sulphurous  acid  (bleached). 
Their  extraction  may  be  effected  in  most  cases  by 
water,  sometimes  also  by  alcohol  or  other  liquids.  As 
some  extractive  substances  in  the  former  section  have 
been  obtained  in  a  crystalline  form,  so  also  crystallized 
coloring  substances  have  been  separated  from  colored 
extractive  matter ;  but  other  coloring  principles,  on  the 
contrary,  are  only  known  in  the  form  of  extracts.  The 
names  which  have  been  given  to  these  coloring  sufc 


593  VEGETABLE    MATTER, 

stances  likewise  terminate  in  ine,  and  are  included 
in  parentheses  in  the  following  list  of  the  most  impor- 
tant vegetable  coloring  matters. 

591.  Red  and  Violet  Coloring  Substances. 

a.)  Madder  is  the  ground-up  root  of  the  Hubia  tinc- 
torum.  The  fresh  root  looks  yellow,  but  when  exposed 
to  the  air  it  becomes  red,  owing  to  the  absorption  of 
oxygen,  and  yields  a  superior  permanent  or  fast  red 
color  in  dyeing,  for  instance,  the  brilliant  Turkey- 
red  ;  also  beautiful  lake  colors,  such  as  madder-lake. 
(Coloring  matter,  Alizarine,  or  madder-red,  crystallizes 
in  yellowish-red  needles,  soluble  in  boiling  water.) 
Madder  contains,  moreover,  a  yellow,  an  orange,  and 
a  brown  coloring  matter. 

b.)  Brazil-wood  (Fernambuca),  from  the  heart- wood 
of  several  trees  growing  in  South  America,  imparts  to 
different  materials  a  beautiful  but  not  very  permanent 
(not  fast)  red  color.  It  is  employed  also  in  the  prep- 
aration of  red  ink,  of  drop-lake,  &c.  (Coloring  matter, 
Braziline,  crystallizes  in  orange-colored  needles,  easily 
soluble  in  water.) 

c.)  Saffloiver,  the  flowers  of  the  dyer's  saffron,  are 
used  for  obtaining  a  brilliant  rose-color  (for  pink-sau- 
cers). (Coloring  matter,  Carlhamine,  soluble  in  water.) 

d.)  The  alkanet-root  contains  in  its  bark  a  resinous 
coloring  matter,  which  is  consequently  not  soluble  in 
water ;  cloth  is  dyed  violet  with  it,  but  alcohol,  oils  (as 
petroleum),  and  fats  (as  lip-salve),  are  colored  pink 
with  it. 

e.)  Sandal-ivood  (red  sanders-wood),  .  the  rasped 
blood-red  wood  of  a  tree  growing  in  the  East  Indies, 
contains  likewise  a  red,  resinous  coloring  matter  (Sa-n* 
taline). 


COLORING    MATTER.  593 

f.)  The  red  dyes  occurring  in  many  fruits,  as,  for 
instance,  cherries,  raspberries,  &c.,  are  but  slightly  du 
rable,  and  only  used  for  coloring  confectionery,  cor- 
dials,  &c. 

#',)  Cochineal  is  a  dried  insect,  which  is  brought  to  us 
from  Mexico.  The  well-known  red  carmine  is  obtained 
from  it,  and  in  dyeing  establishments  a  very  brilliant 
scarlet  and  purple  red  is  prepared  from  it.  ( Cochineal- 
red)  reddish-purple,  crystalline  grains.) 

h.)  Lac-lake,  or  lac-dye,  is  a  reddish-black,  resinous 
mass,  which  is  obtained  in  the  preparation  of  shellac 
(§  570) ;  it  contains  a  red  coloring  matter  very  similar 
to  cochineal-red. 

592.   Yelloiv  Coloring'  Substances. 

a.)  Fustic  is  the  rasped  trunk-wood  of  a  mulberry- 
tree  growing  in  the  West  Indies.  (Marine,  crystallizes 
in  yellow  needles,  soluble  in  water.) 

b.)  Quercitron,  a  nankeen-yellow  powder,  mixed 
with  fibrous  fragments,  is  obtained  from  the  bark  of  the 
black  oak,  a  tree  of  North  America.  ( Quer citrine,  a 
yellow  powder,  soluble  in  water.) 

c.)  Buckthorn,  Persian,  or  yellow  berries  are  the  fruit 
of  the  buckthorn,  growing  in  warm  countries,  and 
gathered  before  they  are  ripe.  (Coloring  matter  only 
known  as  an  extract,  soluble  in  water.) 

d.)  Weld  and  dyer's  weed  are  the  names  given  to  the 
Reseda  luteola,  dried  after  it  has  done  blooming.  (Lu~ 
teoline,  crystallizes  in  yellow  needles,  soluble  in  water.) 

The  four  last-mentioned  coloring  substances  are 
principally  used  for  dyeing  silk,  wool,  cotton,  and  other 
materials,  yellow. 

e.)  Annotto,  orleana,  occurs  as  a  brownish-red  paste, 
v  hich  is  prepared  from  the  puli)  surrounding  the  seeds 
50* 


594  VEGETABLE    MATTER. 

of  the  Bixa  Orellana,  and  contains  two  coloring  princi- 
ples, a  yellow  and  a  red.  The  former  is  dissolved 
when  the  annotto  is  boiled  with  water,  the  latter  on 
boiling  it  with  a  weak  lye  ( Orelline). 

/.)  Turmeric,  the  root  of  a  plant  growing  in  the  East 
Indies,  is  very  rich  in  a  resinous  yellow  dye,  which 
is  colored  brownish-red  by  alkalies.  Paper  stained  with 
it  may  therefore  be  used  like  red  litmus-paper  for  de- 
tecting alkalies.  (Curcumine,  an  amorphous  yellow 
mass.) 

g.)  Saffron  consists  of  the  dried  stigmas  of  the  flow- 
ers of  the  Crocus  sativus.  Its  application,  in  coloring 
articles  of  food  and  cordials  yellow,  is  well  enough 
known.  (Polychroite.) 

593.   Green  Coloring  Substances. 

Leaf-green  (chlorophyll)  is  one  of  the  most  widely 
diffused  substances  in  the  vegetable  kingdom,  since  it 
occurs  in  all  parts  of  the  plant  which  possess  a  green 
color.  As  found  in  plants,  it  is  a  mixture  of  wax  and 
of  several  coloring  matters  not  well  known.  It  need 
hardly  be  said,  that  it  is  not  soluble  in  water ;  for  if  it 
were,  the  water  would  become  green  on  flowing  over 
meadows.  The  expressed  juices  of  the  herbs  are  in- 
deed green,  but  it  is  obvious  from  their  turbidness  that 
the  leaf-green  is  only  mechanically  mixed  with  the 
liquid.  We  become  still  more  fully  convinced  of  this 
by  the  separation  of  the  coloring  matter  which  takes 
place  when  the  juices  are  boiled,  or  allowed  to  remain 
for  some  time  in  repose.  If,  on  the  other  hand,  alcohol, 
ether,  or  weak  lye.  is  poured  on  the  green  leaves,  we 
obtain  green  solutions ;  hence  all  the  tinctures  of  phar- 
macy which  are  prepared  from  leaves  or  stalks  have  a 
green  color.  The  green  color  appears  only  in  those 


COLORING    MATTER.  595 

parts  of  the  plant  which  are  exposed  to  the  light;  it  is 
obvious  from  this,  that  the  chemical  compound  which 
we  call  chlorophyll  is  only  generated  with  the  coopera- 
tion of  light.  When  separated  from  plants,  this  color- 
ing matter  is  very  soon  decomposed ;  it  is,  therefore,  not 
at  all  suited  f6r  a  coloring  substance,  except,  perhaps, 
for  cordials  and  other  liquids.  In  the  autumn  it  is  con- 
verted in  the  leaves  themselves  into  leaf-yellow  and 
leaf-red,  probably  by  a  process  of  oxidation. 

Sap-green  is  an  extract  prepared  from  the  juice  of  the 
buckthorn  berries,  by  the  addition  of  alum. 

594.  Blue  Coloring  Substances. 

Indigo.  —  Several  plants  of  hot  climates  contain  a 
colorless  juice,  from  which,  after  standing  in  the  air  and 
abstracting  oxygen  from  it,  a  blue  sediment  is  depos- 
ited, that,  when  dried,  forms  the  well-known  indigo. 
This  substance,  very  important  to  science  and  the  arts, 
usually  occurs  in  commerce  in  deep  blue,  friable  cakes, 
which  exhibit,  when  rubbed  by  the  nail,  a  coppery 
color  and  lustre.  Its  brilliant  blue  coloring  matter  is 
called  indigo-blue;  but  besides  this,  the  crude  indigo 
contains  other  foreign  substances,  such  as  indigo-gluten, 
indigo-brown,  indigo-red.  • 

Indigo  is  quite  insoluble  in  water,  alcohol,  ether,  &c. ; 
there  is  only  one  liquid  known  which  can  dissolve  it, 
fuming  sulphuric  acid  (§  170).  The  indigo-blue  chem- 
ically combines  with  the  sulphuric  acid,  forming  a  blue 
compound  soluble  in  water,  which  is  called  sulphin- 
digotic  acid.  What  we  call  tincture  of  indigo  is  prin- 
cipally a  mixture  of  water,  sulphindigotic  acid,  and  free 
sulphuric  acid. 

The  sulphindigotic  acid  combines  like  a  simple  acid 
with  bases,  forming  salts.  The  best  known  of  these 


596  VEGETABLE    MATTER. 

salts  is  sulphind isolate  of  potassa  (blue  carmine),  which 
is  obtained  as  a  deep  blue  precipitate  when  the  sulphin- 
digotic  acid  is  neutralized  by  potassa.  The  blue  car- 
mine is  indeed  soluble  in  pure  water,  but  not  in  water 
containing  a  salt  in  solution. 

Deoxidation  of  Indigo.  —  We  can  also,  but  in  a  very 
different  way,  render  indigo  soluble,  by  mixing  it  with 
bodies  which  have  a  very  great  affinity  for  oxygen  ;  for 
instance,  with  protoxide  of  iron,  protoxide  of  tin,  &c. 

Experiment.  —  Triturate  half  a  dram  of  finely  pow- 
dered indigo,  with  half  a  dram  of  green  vitriol,  and 
one  dram  and  a  half  of  slaked  lime ;  shake  up  the 
mixture  in  a  four-ounce  bottle ;  then,  having  filled  the 
bottle  with  water  and  closed  it  tightly,  let  it  stand 
for  several  days ;  the  indigo  gradually  loses  its  blue 
color,  and  dissolves  into  a  clear  yellowish  liquid.  The 
body  which  effects  the  decoloration  is  the  protoxide  of 
iron,  which  is  separated  by  means  of  the  lime  from  the 
green  vitriol.  This  attracts  oxygen  from  the  indigo, 
whereby  the  latter  becomes  colorless  and  soluble  in 
lime-water  (reduced  indigo).  As  soon  as  the  clear 
liquid  is  exposed  to  the  air,  it  again  attracts  oxygen  and 
becomes  blue.  If  you  saturate  a  piece  of  blotting-paper 
with  the  liquid,  and  then  «lry  it  in  the  air,  it  first  be- 
comes green,  and  then  blue,  and  the  blue  color  formed 
adheres  quite  firmly,  since  it  has  not  only  settled  upon 
but  in  the  fibres  of  the  paper.  In  dyeing  establish- 
ments, such  a  solution  of  indigo  is  called  the  cold  vat. 
A  third  method  of  rendering  indigo  soluble  is  by  add- 
ing it,  together  with  hot  water,  to  a  mixture  of  bran, 
woad,  madder,  &c.,  which  (carbonate  of  potassa  and 
lime  being  present)  passes  into  'fermentation.  The 
fermentation  is  partly  acid,  and  partly  putrid  ;  in  both 
processes  oxygen  is  required,  which  is  in  part  taken 


COLORING    MATTER. 


597 


from  the  indigo.  The  deoxidized,  colorless  indigo  dis- 
solves in  the  alkaline  liquid  (warm  vat).  By  treating 
indigo  with  bodies  which  readily  part  with  oxygen,  for 
instance,  with  nitric  acid,  chromic  acid,  &c.,  we  have 
in  modern  times  become  acquainted  with  some  very 
interesting  products  of  oxidation  (isatine,  isatinic  acid, 
anilic  acid,  picric  acid,'  &c.). 

Woad  is  a  European  plant,  which  likewise  contains 
indigo,  but  in  far  less  quantities  than  the  foreign  in- 
digo plants. 

Log- wood,  or  Campeachy-wood,  the  reddish-brown  in- 
terior wood  of  a  tree  of  tropical  America,  is  one  of  the 
most  common  coloring  matters  for  dyeing  blue,  violet, 
and  black.  (Hcematoxyline,  in  yellowish  crystals,  which 
become  speedily  violet  and  blue  in  the  air,  owing  to  the 
ammonia  always  contained  in  the  latter.) 

Archil.  —  Several  species  of  lichens,  growing  on  the 
rocks  in  England  and  France,  contain  peculiar  sub- 
stances (orcine,  erythrine,  &c.),  which,  although  in 
themselves  colorless,  acquire  a  beautiful  purple-red  color 
when  they  are  acted  upon  by  ammonia.  It  is  com- 
mon to  putrefy  the  bruised  lichens  with  urine,  and 
then  a  red  or  violet-colored  paste  is  obtained  (cudbear ', 
pe.rsiO)  orchil).  By  the  addition  of  lime  or  potassa,  this 
red  is  changed  into  blue  (litmus).  We  have  examples 
of  both  these  coloring  matters  in  red  and  blue  test- 
paper. 

595.  Experiments  with  Coloring  Substances. 

Experiment  a.  —  Take  up  some  sandal-wood  on  the 
point  of  a  knife  and  put  it  on  a  filter,  and  pour  over  it 
some  alcohol ;  the  alcohol  which  passes  through  has  a 
red  color,  and,  when  poured  upon  a  piece  of  wood,  im- 
parts to  it  an  intense  blood-red  color.  Cabinet-makers 


598  VEGETABLE    MATTER. 

frequently  employ  this  solution  for  staining  furniture. 
Alcohol  acquires  a  pink  color  when  a  small  piece  of 
alkanet-root  is  put  into  it.  Water  will  not  extract  a 
red  dye  from  either  of  these  substances.  Those  color- 
ing matters  which  are  soluble  only  in  alcohol  are  called 
resinous. 

Experiment  b.  —  Boil  for  some  time  in  a  jar,  —  1st, 
Fig.  216.  French  berries ;  2d,  Brazil-ivoo^l ; 

and  3d,  logwood ;  each  separately, 
with  twelve  times  its  amount  of 
water ;  the  decanted  decoction  of 
the  first  is  yellow,  of  the  second 
reddish-yellow,  and  of  the  third 
brownish-red ;  a  sufficient  proof 
that  the  coloring  matters  con- 
tained in  these  substances  have  been  dissolved  in  the 
water.  Dyers  call  these  colored  decoctions  baths. 

Experiment  c.  —  Divide  these  coloring  decoctions  into 
two  equal  parts.  Dissolve  a  quarter  of  an  ounce  of 
alum  in  one  of  each  of  the  parts,  and  then  add  to  them 
a  solution  of  carbonate  of  potassa,  as  long  as  any  pre- 
cipitate subsides.  As  was  stated  in  §  260,  the  hydrate 
of  alumina  is  precipitated ;  but,  together  with  this,  the 
coloring  matter  is  also  precipitated,  and  hence  the  pre- 
cipitates are  colored.  These  precipitates  are  called 
lakes.  The  lake  obtained  from  the  French  berries  oc- 
curs in  commerce  under  the  name  of  yellow  lake,  that 
from  Brazil-wood  as  drop-lake. 

Experiment  d.  —  Prepare  a  solution  of  alum  (&), 
another  of  salt  of  tin  (b),  a  third  of  green  vitriol  (c),  a 
fourth  of  carbonate  of  potassa  (d),  a  fifth  of  tartaric  acid 
(e),  and  saturate  a  sheet  of  white  blotting-paper  with 
each  solution.  When  dry,  cut  each  sheet  into  three 
ptrips,  smear  one  of  the  strips  from  each  sheet  with  the 


COLORING    MATTER.  599 

berries,  another  of  them  with  the  Brazil-wood,  and  the 
third  set  with  the  logwood  decoction,  and  again  dry 
them.  You  will  find  that  one  and  the  same  coloring 
matter  produces  a  different  color,  or  shade  of  color,  upon 
each  of  the  five  sheets.  This  color  will  be  very  slight 
when  the  colored  decoctions  are  applied  to  mere  blot- 
ting-paper (/).  If  you  now  immerse  the  colored  and 
^ied  strips  in  warm  water,  the  colors  will  be  for  the 
most  part  dissolved  from  the  three  last  tests  (d,  e,f), 
but  not  from  the  former  (a,  b,  c).  Those  salts  which, 
like  alum,  salt  of  tin,  and  green  vitriol,  have  the  power 
of  forming  insoluble  combinations  with  the  coloring 
matters,  and  fixing*  them  firmly  in  the  fibres  of  the 
cloth,  are  called  mordants,  and  are  generally  employed 
in  dyeing  and  calico-printing  establishments,  to  fix  the 
dyes  upon  the  various  materials,  such  as  silk,  wool,  cot- 
ton, linen,  &c.  That  which  effects  the  coloring  is  an 
insoluble  lake  color,  that  is,  a  combination  of  the  color- 
ing matter  with  alumina,  peroxide  of  tin,  or  sesquioxide 
of  iron,  but  which,  in  order  that  it  may  adhere  firmly, 
must  first  be  formed  within  the  pores  of  the  vegetable 
fibre.  If  it  is  formed  on  the  outside  of  them,  it  only 
covers  the  fibres  externally,  and  then  merely  adheres 
mechanically  upon  them ;  such  a  color  may  be  removed 
from  the  material  by  rubbing,  shaking,  and  also  by 
washing. 

The  process  pursued  in  the  printing'  of  calico,  &c.,  is 
very  similar,  with  this  difference,  however,  that  trie 
mordants  are  only  applied  in  spots,  or  else  the  whole  of 
the  cloth  is  first  covered  with  the  mordant,  which  is 
again  removed  in  spots  (§  197).  When  a  piece  of  cloth 
thus  treated  is  immersed  in  the  coloring  decoction,  the 
coloring  matter  will  be  precipitated  only  in  those  places 
covered  with  the  mordant,  and  thus,  instead  of  one  un- 


600 


VEGETABLE  MATTER. 


interrupted  homogeneous  color,  an  interrupted  color  is 
obtained,  presenting  a  pattern. 


XIV.   ORGANIC  BASES,  OR  VEGETABLE 
BASES    (ALKALOIDS). 

596.  IT  has  already  been  mentioned,  under  the  head 
of  extractive  matter,  that  many  plants  contain  peculiar 
substances,  which,  like  the  inorganic  bases,  can  combine 
with  acids,  forming  salts ;  they  are  called  organic  bases. 
Many  of  them,  also,  like  the  alktlies,  exert  a  basic  re- 
action upon  red  test-paper ;  hence  the  second  name,  al- 
kaloids. The  organic  bases  are  to  the  inorganic  bases 
what  the  organic  acids  are  to  the  inorganic  acids. 
The  organic  bases  are  composed  of  two,  commonly  of 
four  elements  (carbon,  hydrogen,  oxygen,  and  nitrogen), 
the  inorganic  of  two  elements  only ;  they  are  charred 
and  consumed  by  heat, — the  inorganic  bases  are  not; 
they  undergo,  in  the  presence  of  water  and  heat,  a  pu- 
trefactive decomposition,  —  the  inorganic  bases  do  not. 
They  are  characterized  by  containing,  almost  without 
exception,  nitrogen  in  their  composition. 

Almost  all  organic  bases  dissolve  with  difficulty,  or 
not  at  all,  in  water,  but  more  readily  in  alcohol',  their 
solutions  have  commonly  a  very  bitter  taste.  As  a 
general  rule,  they  dissolve,  when  combined  with  acids 
as  salts  much  more  easily  in  water,  than  they  do  when 
in  their  simple  condition. 

Most  of  the  organic  bases  known  at  present  are  de- 
rived from  those  plants  which  are  characterized  by  their 
poisonous  qualities  or  by  their  medicinal  effects,  and 
we  have  strong  reasons  for  attributing  to  them  the  poi~ 


ORGANIC    BASES.  601 

sonous  and  medicinal  properties  of  the  plants  Many  of 
them  are  virulent  and  dangerous  poisons;  but  in  very 
small  doses  they  are  energetic  medicines.  One  grain 
frequently  possesses  the  same  medicinal  power  as  an 
ounce,  or  even  several  ounces,  of  the  vegetable  sub- 
stances from  ^bich  they  were  obtained. 

The  vegetable  bases,  when  they  are  dissolved,  are 
Almost  without  exception  precipitated  by  tannic  acid  as 
nearly  or  entirely  insoluble  tannates,  for  which  rea- 
son liquids  containing  tannic  acid,  such  as  tincture  of 
gall-nuts,  decoction  of  green  tea,  or  of  oak-bark,  &c., 
are  not  only  employed  as  reagents  for  detecting  vege- 
table bases,  but  also  as  efficient  antidotes  in  cases  of 
poisoning  by  them. 

The  vegetable  bases  occur  generally  in  combination 
with  vegetable  acids.  They  are  separated  from  these 
acids,  and  extracted  from  the  vegetable  matter,  by  add- 
ing to  the  latter  some  water,  and  an  acid  which  is 
stronger  than  the  vegetable  acid  and  forms  with  the 
base  an  easily  soluble  salt  (muriatic  acid,  sulphuric 
acid,  &c.).  If  an  inorganic  base  (potassa,  lime,  ammo- 
nia, magnesia,  &c.)  is  added  to  the  acid  solution,  the 
organic  base  is  then  precipitated.  But  there  are  also 
numerous  other  methods  of  preparing  these  bases  ;  all 
of  them,  however,  are  long  and  complicated,  for  the 
reason  that  many  other  substances  are  also  extracted 
from  the  plants  at  the  same  time  with  the  bases,  which, 
in  very  many  cases,  can  be  separated  and  purified  only 
by  laborious  operations. 

597.  Some  of  the  most  important  organic  bases 
are  :  — 

Aconiline,    from    the    Aconitum   napellus    (monk's- 
hood),  a  white,  granular  powder,  extremely  poisonous; 
•gV  of  a  grain  will  kill  a  sparrow. 
51 


602  VEGETABLE     MATTER. 

Atropine,  from  the  root  of  the  belladonna  (deadly 
nightshade) ;  it  crystallizes  in  white  silky  prisms ;  very 
poisonous. 

Chelidonine,  from  the  celandine ;  crystallizes  jn  color- 
less tables. 

Quinine  is  found  combined  with  kinic  acid,  chiefly  in 
the  crown-bark  and  in  the  Calisaya-bark,  and  crystal- 
lizes in  silky  needles  ;  but  it  also  occurs  under  the  name 
of  quinoidine  in  the  amorphous  state,  as  a  dark-brown 
resinous  mass,  and  is  a  very  important  medicine.  The 
basic  sulphate  of  quinine,  which  occurs  in  white  needles, 
is  most  commonly  used  in  medicine.  This  is  very 
difficultly  soluble  in  water,  but  is  very  readily  dissolved 
in  it  when  sufficient  sulphuric  acid  is  added  to  convert 
it  into  neutral  sulphate  of  quinine.  Another  base,  very 
similar  to  quinine,  occurs  in  the  gray  cinchona-bark ;  it 
crystallizes  in  white  prisms,  and  has  received  the  name 
citichonine. 

Caffeine^  or  theine,  from  the  unroasted  coffee-bean,  or 
the  so-called  green  tea ;  crystallizes  in  fine  white  prisms 
of  a  silky  lustre. 

Colchicine,  from  meadow-saffron ;  crystallizes  in  white 
needles ;  it  causes,  when  taken,  the  most  violent  vomit- 
ing. 

Daturine,  from  the  seeds  of  the  thorn-apple,  in  color- 
less crystals ;  highly  poisonous. 

Emetine  (from  ipecacuanha)  occurs  when  pure  as  a 
white  powder,  when  impure  as  a  brown  extract ;  a 
powerful  emetic. 

Hyoscyamine,  from  henbane,  in  radiated  groups  of 
whiffe  needles ;  a  narcotic  poison. 

The  Alkaloid  of  Opium.  About  forty  years  ago  the 
first  vegetable  base  was  discovered  in  opium, — the  in- 
spissated juice  of  the  poppy,  —  and  was  called  morphine. 


ORGANIC    BASES.  605 

It  exists  in  opium  combined  with  meconic  acid,  and 
crystallizes  in  colorless  prisms ;  narcotic  and  poisonous ; 
in  small  doses,  a  very  valuable  remedy.  The  acetate 
or  morphine*  is  much  used  in  medicine.  By  later 
investigations  there  have  also  been  found  in  opium 
pseudo-morphine,  narcotine,  narceine,  codeine,  and  the- 
baine. 

Piperine,  from  white,  black,  and  long  pepper;  in 
white  crystalline  needles. 

Solanine,  from  several  species  of  the  solanum,  par- 
ticularly from  the  white  sprouts  of  the  potato;  as  a 
white  powder,  or  in  crystalline,  colorless  needles;  a 
narcotic  poison. 

Strychnine,  from  the  nux-vornica  (the  seeds  of  the 
Strychnos  nux-vornica),  and  from  the  Indian  arrow- 
poison  ;  crystallizes  in  prisms  or  octahedrons ;  very 
poisonous.  There  is  another  base,  Interne,  occurring 
along  with  it. 

Ve.ratrine,  from  white  hellebore,  and  the  seeds  of  the 
sabadilla;  a  lustrous  white  powder,  extremely  poison- 
ous; when  introduced  into  the  nostrils,  it  excites  the 
most  violent  sneezing;  jV  °f  a  grain  will  kill  a  cat. 

The  following  are  volatile  and  liquid  :  — 

Conicine,  from  hemlock,  principally  from  the  seeds ; 
a  colorless  oily  liquid,  of  a  nauseous,  strong  odor ;  very 
poisonous. 

Nicotine,  from  the  leaves  of  the  tobacco,  colorless, 
oily,,  having  a  smell  like  that  of  tobacco.  Highly  poi- 
sonous ;  one  fourth  of  a  drop  will  kill  a  rabbit. 

Vegetable  bases  may  also  be  artificially  produced,  for 
instance,  — 

Aniline,  from  indigo,  or  from  pit-coal  tar. 

Sinammine,  from  mustard.,  &c. 

*  In  this  country  the  sulphate  is  most  generally  employed. 


604  VEGETABLE     MATTER. 


RETROSPECT  OF  THE  EXTRACTIVE  AND   COLORING 
SUBSTANCES,  AND   OF  THE   VEGETABLE  BASES. 

1.  Besides  the  generally  diffused  vegetable  substances 
there  occur  in  almost  every  plant  peculiar  principles, 
upon  which,  in  many  cases,  the  effect,  taste,  and  color, 
of  these  plants  depend. 

2.  We  find  these  peculiar  principles  mixed  with  va- 
rious other  substances  in  the  inspissated  vegetable  juices, 
the  so-called  extracts. 

3.  Many  of  them  are  non-azotized,  others  azotized, 
and  still  others  contain  at  the  same  time  sulphur. 

4.  Those   combinations   which    are   indifferent,  and 
have  no  prominent  color,  are  called  extractive  matter  ; 
they  are  also  called  bitter-extractive,  because  they  have, 
for  the  most  part,  a  bitter  taste. 

5.  Coloring  matter  is  extractive  matter  which  has  an 
absolute  inherent  color,  or  is  converted  by  the  action  of 
other  bodies  into  colored  combinations ;  it  is  quickly 
rendered  colorless  by  chlorine,  slowly  by  light  and  air 
(bleached). 

6.  Coloring  matter  presents  a  great  affinity  for  some 
bases,  especially  for  alumina,  sesquioxide  of  iron,  and 
peroxide   of  tin,  and  forms   with   them  insoluble  col- 
ored compounds  (lake-colors) ;   in  dyeing  and  calico- 
printing  these  insoluble  precipitates  are  produced  in  the 
fibres  of  the  yarn  or  material. 

7.  The  vegetable  bases  can,  like  potassa  or  soda,  com- 
bine with  acids,  forming  salts;  many  of  them  also  exert 
an  alkaline  reaction;  most  of  them  are  difficultly  sol- 
uble in  water,  but  easily  soluble  in  alcohol. 

8.  The  vegetable  bases  occur  principally  in  those  plants 
which  are  characterized  by  particular  poisonous  or  medi- 
cinal qualities.    Many  of  them  are  very  violent  poisons 

9.  Almost  all  vegetable  bases  contain  nitrogen. 


ORGANIC    ACIDS.  605 


XV.   ORGANIC   ACIDS.       , 

598.  THE  organic  acids  are  found  much  more  fre- 
quently, and  in  greater  abundance,  than   the  organic 
bases,  in  the  vegetable  kingdom.     Several  of  them  occur 
uncombined,  or  as  acid  salts  ;  hence  the  acid  taste  which 
we  perceive  in  so  many  vegetable  substances,  especially 
in  unripe  fruits.     They  are  frequently,  also,  completely 
neutralized  by  bases,  or  are  insoluble,  as  in  the  resins, 
and  in  both  these  cases  they  are  not  recognized  by  the 
taste.     Besides  these  acids  ocdurring  in  nature,  many 
also  have  been  discovered,  which  may  be  artificially  pro- 
duced from  other  non-acid  vegetable  substances ;  thus, 
oxalic  acid  and  formic  acid  are  prepared  from  sugar, 
acetic  acid  from  alcohol,  the  fat  acids  from  fats,  &c. 
The  general  properties  of  these  acids  have  already  been 
mentioned  (§  193,  &c.) ;  we  shall  here  notice  only  those 
which  are  best  known. 

599.  Racemic  acid  occurs  in  the  juice  of  many  grapes, 
and  crystallizes  like  tartaric  acid,  to  which  it  is  very 
similar,  in  colorless,  very  acid-tasted  prisms. 

600.  Citric  acid  exists  in  the  juice  of  lemons,  and 
also  in  that  of  currants,  gooseberries,  and  many  other 
fruits.     By  evaporating  the  juice  of  the  lemon,  we  only 
obtain  an  acid  brown  extract,  because  all  the  other  non- 
volatile constituents,  as  well  as  the  citric  acid,  remain 
behind ;  but  if  the  juice  is  neutralized  with  chalk,  a 
difficultly  soluble  citrate  of  lime  is  precipitated,  while 
the  foreign  substances  remain  for  the  most  part  in  solu- 
tion.    We  obtain  from  citrate  of  lime,  by  decomposi- 
tion with  diluted  sulphuric  acid,  gypsum  and  a  solu- 
tion of  citric  acid,  which  yields  on  evaporation  colorless 
prismatic  crystals.      A  mixture  of  the  pleasant  acidu« 

51* 


606  VEGETABLE     MATTER. 

lous-tasting  citric  acid  (or  tartaric  acid)  with  sugar  ia 
called  'lemonade-powder.  By  moderate  heating,  the 
citric  acid  passes  into  aconitic  acid,  an  acid  which  also 
occurs  native  in  monk's-hood. 

601.  Malic  acid  is  obtained  from  sour  apples,  ber- 
ries of  the  mountain-ash,  and  many  other  plants;   it 
is  very  deliquescent,  and  therefore  is  difficult  of  crys- 
tallization.    Malic,  citric,  and   tartaric  acids  are  found 
associated  together  in  almost  all  acid  fruits. 

602.  Formic  acid  occurs  in  ants,  but  may  be  arti- 
ficially  produced   from  almost   all   vegetable   matters, 
when  they  are  treated  with  bodies  rich  in  oxygen ;  for 
instance,  nitric  acid,  chromic  acid,  black  oxide  of  man- 
ganese, or  sulphuric  acid.     It  is  a  volatile,   colorless 
liquid,  of  a  very  acid  taste,  and  a  very  pungent  odor. 

603.  Tannic  acid  (tannin)  is  the  general  name  given 
to  that  substance,  of  very  frequent  occurrence  in  plants, 
especially  in  the  barks  of  trees,  which  imparts  to  them 
the  well-known  puckering  and  astringent  taste.     It  is 
regarded  as  an  acid,  because  it  has  an  acid  reaction,  and 
can  combine  with  bases.     These  acids  are  divided,  ac- 
cording to  the  plants  in  which  they  occur,  into  querci- 
tannic,  mimotannic,  &c.  acids.     The  quercitannic  acid, 
which  is  found  most  abundantly  in  nut-galls  and  in  the 
bark  of  young  oak-trees,  is  best  known.     In  the  pure 
state  it  forms   a  white    or   yellowish   gum-like   mass, 
which  is  very  easily  dissolved  in  water  and  alcohol. 
It  forms  the  principal  constituent  in  the  tincture  of  nut- 
galls.     There  are  two  properties  which  especially  char- 
acterize tannic  acid,  and  have  stamped  it  as  an  ex- 
tremely important  substance  in  the  arts :  — 

a.}  It  yields,  with  salts  of  sesquioxide  of  iron,  a 
blue-black  precipitate  of  tannate  of  sesquioxide  of  iron 
(§  285),  and  therefore  is  generally  employed  for  dyeing 


ORGANIC    ACIDS.  607 

all  kinds  of  materials  with  a  gray  or  black  color,  and  for 
the  preparation  of  ink,  &c. 

b.)  It  combines,  moreover,  with  the  skin  of  animals, 
forming  a  combination  insoluble  in  water,  and  no 
longer  subject  to  putrefaction, —  leather;  hence  the 
name  tannin,  and  hence  the  extensive  application  of 
the  vegetable  substances  containing  tannin  (bark  of  the 
oak,  pine,  birch  trees,  &c.)  in  the  tanner's  trade. 

604.  If  a  solution  of  tannic  acid  remains  for  a  long 
time  exposed  to  the  air,  it  will  be  converted  into  two 
new  acids,  gallic  and  ellagic  acids.    Consequently,  both 
are  to  be  found  in  tincture  of  nut-galls,  and  in  ink, 
which  have  been  kept  for  some  length  of  time.     Gallic 
acid  crystallizes  in  white  needles  or  prisms ;  its  solution 
yields,  like  tannic  acid,   a  blue-black  precipitate  with 
salts  of  sesquioxide  of  iron,  but  it  does   not  tan  the 
skins  of  animals. 

605.  Substances  containing  Tannin.  —  The  following 
are  the   principal  dye-stuffs    and   tanning    substances 
which  occur  in  commerce. 

a.)  Nut-galls.  They  are  produced  on  oak-leaves  by 
the  puncture  of  an  insect.  The  best  come  from  Asia 
Minor,  and  consist  nearly  one  half  of  tannic  acid;  in- 
ferior sorts  are  brought  from  Italy  and  Hungary.  The 
nut-galls  formed  on  trees  in  Germany  contain  but  little 
tannic  acid. 

b.)  Catechu,  the  brown,  dry  extract  of  the  Acacia 
catechu,  is  now  very  frequently  used  in  dyeing  and 
calico-printing  establishments,  for  the  production  of  a 
brown  color ;  sometimes,  also,  for  tanning  skins. 

c.)  Kino,  the  brownish-black  extract  of  a  tree  grow- 
ing in  the  East  Indies. 

d.)  Sumach,  or  Rhus,  the  bruised  leaves  of  several 
kinds  of  rhus  ;  very  important  in  dyeing. 


608  VEGETABLE    MATTER. 

e.)  Divi-divi,  the  seed  capsules  of  an  African  plant, 

/.)  Bablah,  the  pods  of  a  species  of  mimosa  growing 
in  the  East  Indies. 

g.)  The  rind  of  the  pomegranate,  rind  of  the  walnut, 
&c.,  &c. 

606.  The  acids  just  mentioned,  together  with  tar- 
taric,  oxalic,  and  acetic  acids,  previously  treated  of,  are 
very  widely  diffused ;  but  besides  these  there  are  many 
others,  which  are  found  only  in  particular  plants  or 
vegetable  substances,  or  are  artificially  prepared  from 
them ;  as,  — 

Succinic  acid,  in  amber ;  white  crystals,  volatile  in  the 
heat ;  it  is  formed  also  by  the  oxidation  of  stearic  acid. 

Ben-zoic  acid,  in  benzoin ;  white  crystalline  needles, 
volatile  in  the  heat ;  it  is  formed  also  in  many  ethereal 
oils,  when  long  kept.  The  bitter  oil  of  almonds,  on 
exposure  to  the  air,  is  oxidized,  and  completely  convert- 
ed into  crystallized  benzoic  acid. 

Cinnamic  acid,  in  old  oil  of  cinnamon  and  in  balsam 
of  Peru  ;  white  crystals. 

Caryophyllic  acid,  in  the  oil  of  cloves ;  an  oily  liquid. 

Valerianic  acid,  in  the  root  of  valerian  ;  an  oily  liquid 
of  a  pungent  odor.  May  be  prepared,  also,  from  the 
fusel  oil  of  potatoes. 

Suberic  acid  is  prepared  by  heating  cork  or  fat  acida 
with  nitric  acid. 

Fumaric  acid,  in  fumitory  and  in  Iceland  moss ;  it  is 
formed  also  by  heating  malic  acid. 

Chelidonic  acid,  in  celandine. 

Me  conic  acid,  in  opium. 

Kinic  acid,  in  cinchona-bark. 

Lactic  acid,  in  whey,  sour-krout,  juices  of  flesh,  &c. 

Uric  or  lithic  acid,  in  urine,  &c. 


ASHES.  609 

XVI.    INORGANIC   CONSTITUENTS    OF 
PLANTS   (ASHES). 

607.  IF    we   review   the   proximate   constituents    of 
plants  treated  of  in  the  preceding  section,  it  will  be 
seen  that  they  are  composed  either  of  three  elements 
(C,  H,  O),  or  of  four  elements  (C,  H,  O,  N).    We  may 
accordingly  regard  the  organogens,  carbon,   hydrogen, 
oxygen,  and  nitrogen,  as  the  four  main  pillars   of  the 
vegetable  world.     Next  to  them,  sulphur  and  phospho- 
rus appear  widely  diffused  in  the  vegetable  kingdom, 
since  they  form  essential  constituents  of  the  albuminous 
substance  never  failing  in  any  plant.     But  the  list  of 
the  chemical  substances  occurring  in  plants  is  not  yet 
finished;   for  were  it  so,  plants  would  be  completely 
consumed  by  heat  without  any  thing  being  left  behind. 
But  on  the  combustion  of  every  plant  a  residue  re- 
mains, which   neither  burns  up  nor  volatilizes ;  conse- 
quently there  must  also  be  present,  besides  the  combus- 
tible organic  compounds,  some  incombustible  inorganic 
substances.     The  latter  are  termed  ashes. 

608.  The  term  ashes  is  just  as  indefinite  as  that  of  hu 
mus.     Humus  is  the  term  generally  applied  to  all  those 
black  or  brown  substances  formed  during  the  decay  of 
organic  matter ;  but  by  ashes  are  understood  all  the  non- 
volatile and  incombustible  substances  which  remain  be- 
hind after  the  incineration  of  organic  matter.    How  very 
different  these  may  be,  both  in  quantity  and  quality,  is 
obvious  from  even  a  superficial  observation  of  the  three 
best  known  kinds  of  ashes,  those  of  wood,  peat,  and 
pit-coal.    From  a  hundred  pounds  of  wood  we  obtain 
only  half  a  pound,  or  at  most  three  pounds,  of  ashes ; 
from   a   hundred   pounds   of  pit-coal  or  peat,  twenty 
or  thirty  pounds  of  ashes.     Wood-ashes  contain  very 


610  VEGETABLE    MATTER. 

many  parts  soluble  in  water,  pit-coal  and  peat-ashes 
very  few  parts  ;  the  former  yields  with  water  a  power- 
ful alkaline  lye,  the  latter  does  not  ;  the  former  always 
acts  on  our  fields  and  meadows  as  an  excellent  ma 
nure,  the  latter  only  in  a  small  degree.  Great  differ- 
ences also  appear  when  the  ashes  of  other  plants  or 
parts  of  plants  are  compared  with  each  other,  as  may 
be  seen  from  the  following  table  :  — 

Of  which  ara 

soluble  in 
-Yield  water  about 

100  Ibs.  oak-wood  2  to  4  Ibs.  ashes  ;        •}. 

100  "  oak-bark  5  «  6   "  «             -jV 

100  "  oak-leaves  (in  spring)         5   "  «  •£. 

100  «          «            (in  fall)              5£«  «  £. 

100  "  dried  potatoes  8  «  9   «  "              £. 

100  "  potato-tops                         15    "  " 

100  «  wheat-grain  2  "  3   "  « 

100  «  wheat-straw  4  «  6   «  « 


The  quantity,  as  well  as  the  nature,  of  the  inorganic 
matter  in  plants  consequently  varies  in  the  most  re- 
markable manner,  and  not  only  according  to  the  differ- 
ence of  the  plants,  but  according  to  the  difference  of  the 
individual  parts  of  one  and  the  same  plant  ;  indeed,  even 
in  the  latter  according  to  the  difference  of  age.  We 
always  find  the  largest  quantities  of  it  in  the  younger 
A  egetable  organs,  where  the  progress  of  growth  is  most 
active,  namely,  in  the  leaves  and  twigs. 

609.  If  we  ask  what  is  the  constitution  of  vegetable 
ashes,  chemical  analysis  replies,  that  they  consist  prin- 
cipally of  potassa,  soda,  lime,  magnesia,  and  sesquioxidt, 
of  iron,  combined  with  carbonic  acid,  silicic  acid,  phos- 
phoric acid,  sulphuric  acid,  and  muriatic  acid  (chlorine), 
Of  these  combinations  there  are  principally,  — 


ASHES.  611 

a.)  Soluble  in  water,  the  alkaline  salts  (salts  of  po- 
tassa  and  soda). 

b.)  Soluble  in  diluted  muriatic  acid,  the  earthy  salts 
(salts  of  lime,  of  magnesia,  and  of  sesquioxide  of  iron). 

c.)  Insoluble  in  water  and  acids,  the  silicates. 

The  character  of  the  prevailing  inorganic  constitu- 
ents of  a  plant  may  be  ascertained,  though  only  in  an 
approximative  manner,  by  merely  treating  the  ashes 
first  with  water,  and  then  with  diluted  muriatic  acid. 

610.  The    above-named  •  inorganic    substances    are 
often  contained  in  the  living  plants  in  quite  a  different 
form  fro/n  that  in  the  ashes ;  namely,  sulphur  as  a  con- 
stituent of  the  albuminous  matter,  but  the  bases  mostly 
as  vegetable  acid  salts.     That  the  latter  are  converted 
on  ignition  into  carbonates   (carbonate  of  potassa,  of 
soda,  of  lime,  &c.)  has  previously  been  shown  under  the 
heads  of  tartrate  and  oxalate  of  potassa  (§§  194,  197), 
and  thus  is  explained  why  almost  all  ashes  effervesce 
with   acids.     The  sulphur,  on  the  incineration  of  the 
plant,  is  partly  converted  into  sulphurous  acid,  which 
escapes,  and  partly  into  sulphuric  acid,  which  unites 
with  one  of  the  bases  present,  and  remains  behind  in 
the  ashes. 

611.  It  has  already  been  mentioned  under  the  heads 
of  phosphoric  and  silicic  acids  (§§  176,  183),  and  of  po- 
tassa and  lime  (§§  214,  240),  that  these  substances  are 
able  to  exercise  a  very  favorable  influence  upon  the 
growth  of  plants,  and  that  many  plants  will  not  flour- 
ish in  a  soil  in  which  salts  of  potassa  are  wanting,  and 
that  others  will  not  thrive  in  a  soil  which  contains  no 
lime,  or  no  silicates  or  phosphates.     The  occurrence  of 
inorganic  substances   in    all   plants  must  lead  to  the 
conclusion,  that  every  plant  requires  a  certain  qua^.  tity 
of  them  for  its  existence,  and  for  its  complete  develop- 


612 


VEGETABLE  MATTER. 


merit.  If  the  plant  does  not  find  them  in  the  soil  as- 
signed to  it,  it  is  obstructed  in  its  growth ;  it  pines  and 
withers  away,  before  attaining  maturity.  It  is  highly 
probable  that  basic  bodies,  as  lime  and  potassa,  act 
here  in  a  predisposing  manner,  similar  to  that  in  the 
formation  of  nitric  acid ;  that  they  effect  by  their  pres- 
ence the  formation  of  organic  acids,  with  which  they 
afterwards  enter  into  combination.  On  the  further 
growth  and  ripening  of  the  plants,  there  are  formed,  as 
it  appears,  from  these  acids,  the  indifferent  substances 
starch,  gugar,  gum,  &c. ;  for,  as  is  well  known,  the  acid 
taste  is  lost  in  many  vegetable  parts,  especially  in  the 
fruits  at  the  time  of  ripening,  while  a  mealy,  sweet,  or 
mucilaginous  taste  'supplies  its  place. 

It  follows  from  what  has  previously  been  stated,  that 
the  inorganic  salts  requisite  for  the  growth  of  each  indi- 
vidual plant,  may  be  ascertained  most  simply  by  burn- 
ing the  plant,  and  examining  the  ashes  which  remain ; 
it  requires  the  same  substances  which  are  found  in  its 
ashes.  If  we  now  examine  the  soil  on  which  plants  ot 
this  kind  are  to  be  cultivated,  we  shall  find  by  compar- 
ison which  of  the  constituents  of  the  ashes  are  already 
present  in  it,  and  what  constituents  must  be  added  to 
it  that  the  plants  may  find  therein  all  the  mineral  sub- 
stances requisite  for  their  development  and  growth. 

612.  Arable  land,  or  arable  soil,  that  is,  the  upper  thin 
layer  of  the  surface  of  our  earth,  in  which  plants  ger- 
minate and  take  root,  consists  chiefly  of  two  different 
kinds  of  matter ;  namely,  inorganic  substances,  belong- 
ing to  the  mineral  kingdom  (silica,  combinations  of 
silicic,  phosphoric,  carbonic,  and  sulphuric  acids  with 
alumina,  lime,  magnesia,  potassa,  soda,  and  iron),  and 
organic  substances,  derived  from  the  animal  and  vege- 
table kingdom  (humus-like  substances). 


ASHES. 


The  ground  and  soil  which  are  adapted  to  vegetation 
are  principally  formed  of  mineral  substances,  more  or  less 
finely  divided,  which  consist  of  rocks  that,  have  been 
disintegrated  by  the  operation  of  the  atmosphere,  or 
weathered,  during  the  lapse  of  centuries  (§  265).  This 
weathering  fs  going  on  uninterruptedly,  even  now,  in 
the  soil  of  the  earth,  and  so  much  the  more  rapidly  in 
proportion  as  the  soil  is  loosened  and  penetrated  by  air 
and  water  (fallow).  But  during  this  process,  the  masses 
of  rock  are  not  merely  mechanically  broken  into  small 
fragments,  but  they  are  also  chemically  changed,  since 
from  their  several  insoluble  constituents  soluble  salts  — 
for  instance,  salts  of  potassa,  soda,  lime,  &c.  —  are  gen- 
erated, which  may  be  absorbed  by  the  roots  of  the 
plants.  Every  thing  which  promotes  the  weathering 
and  dissolution  of  the  rocks  —  for  instance,  burning 
of  the  soil  (§  258),  mixing  it  with  lime  (§  240)  or  acids 
(§§  173,  186,  &c.)  —will  accordingly,  as  a  general  rule, 
exercise  a  beneficial  influence  upon  the  growth  of 
plants. 

The  organic  substances  contained  in  arable  soil  have 
always  a  brown  or  black  color,  and  are  designated  by 
the  general  term  humus  (§  444).  They  partly  consist 
of  decaying  leaves  and  branches,  which  have  fallen  off, 
anri  of  decaying  roots  of  plants  remaining  behind  in 
the  earth,  and  partly  of  decomposing  vegetable  or  ani- 
mal manure  put  upon  the  soil.  It  has  already  been 
previously  mentioned,  that  these  products  of  decay  are 
gradually  still  further  decomposed  into  carbonic  acid, 
ammonia,  and  water,  and  for  this  reason  cause  a  more 
vigorous  growth  of  the  plant.  They  likewise  act  favor-, 
ably  on  vegetation,  because  by  reason  of  their  dark 
color  the  soil  is  heated  more  strongly  by  the  rays  of  the 
sun,  Vcause  they  loosen  the  soil,  and  finally,  because 
52 


614  VEGETABLE    MATTER. 

the  weathering  of  the  rocks  is  promoted  by  the  caroonic 
acid  which  is  set  free  from  them. 


XVII.     NOURISHMENT  AND  GROWTH  OF 
PLANTS. 

*3 

s 

Electricity, 
.tf 

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cT 

_ 

^ 

a 

1 

1- 

1 

>-^ 

I 

d          d          W          £ 

Silica,  Alumina,  Lime,  Salts,  Humus. 

613.  Carbon,  oxygen,  hydrogen,  and  nitrogen,  —  these 
are  the  four  elements  which  the  Divine  Power  has 
established  as  main  pillars  for  the  structure  of  the 
whole  organic  creation  ;  from  them,  and  also  from  sul- 
phur, phosphorus,  and  some  other  inorganic  substances, 
all  the  numberless  wonderful  forms  of  the  animal  and 
vegetable  world  are  produced.  We  as  yet  know  but 
little  about  the  interior  chemical  workings  by  which 


GROWTH    OF    PLANTS-  615 

these  results  are  effected,  but  we  have  nearly  ascer- 
tained the  external  conditions  under  which  they  take 
place,  and  the  sources  from  which  the  above-named 
elementary  substances  are  taken. 

That  plants  require  for  their  germination  and  devel- 
opment soil,  *  water,  air,  warmth,  and  light  —  those 
universal  conditions  of  vegetable  life  —  is  well  enough 
known;  while  the  chemical  investigations  of  modern 
times,  and  particularly  those  instituted  by  Liebig,  have 
first  diffused  a  clearer  light  as  to  what  single  constitu- 
ents are  taken  up  from  the  earth,  the  water,  and  the  air 
by  the  plants,  and  serve  them  as  means  of  nourishment. 

UNCULTIVATED  PLANTS  (MEADOWS,  FORESTS,  &c.). 

614.  Food  of  Plants.  —  Plants  absorb  their  nourish- 
ment partly  by  the  roots,  partly  by  the  leaves.  It  fol- 
lows from  this,  that  the  nourishment  must  either  be 
liquid  or  aeriform ;  for  in  these  two  forms  only  can  it 
penetrate  into  the  fine  pores  of  the  root-fibres  and 
leaves.  Plants  receive  their  hydrogen  and  oxygen  from 
the  water,  their  carbon  from  carbonic  acid,  their  nitrogen 
principally  from  ammonia,  their  inorganic  constituents 
chiefly  from  the  earth.  Water,  carbonic  acid,  ammonia, 
and  a  small  number  of  inorganic  salts,  are  accordingly 
to  be  regarded  as  the  nourishment  of  plants. 

a.)  Water  furnishes  the  plants  with  oxygen  and  hy- 
drogen.—  The  plants  imbibe  it  as  a  liquid,  by  their 
roots,  from  the  earth,  and  as  vapor,  through  their  leaves, 
from  the  air.  Water  is  moreover  essential  to  plants,  in 
so  far  as  it  occasions,  by  its  fluid  condition,  the  for-1 
mation  of  the  solid  vegetable  parts ;  for  all  the  soliu 
ingredients  of  the  plants  are  developed  from  the  juice, 
rendered  liquid  by  water. 


616  VEGETABLE    MATTER. 

b.)  Carbonic  acid  furnishes  the  plants  with  carbon. 
—  This  is  principally  absorbed  (§  167)  by  the  leaves 
from  the  air,  which  is  constantly  supplied  with  it  by  the 
processes  of  combustion,  decay,  and  respiration.  More- 
over, the  roots  of  the  plants  find  carbonic  acid  in  every 
soil  which  contains  humus,  for  humus  consists  of  de- 
caying organic  matter,  that  is,  organic  matter  resolving 
itself  into  carbonic  acid  and  water  (§444).  From  this 
limited  source  the  young  plants  especially  draw  their 
nourishment,  before  they  have  leaves  enough  by  means 
of  which  to  appropriate  to  themselves  the  carbonic  acid 
from  the  free  air.  The  changes  which  the  latter  under- 
goes by  the  action  of  living  plants  are  shown  in  the  fol- 
lowing experiments :  — 

Experiment.  —  Fill  a  glass  funnel  with  the  fresh 
leaves  of  some  plant,  and  invert  it 
in  a  wide  glass  vessel  filled  with 
water,  in  such  a  manner  as  quite  to 
cover  the  funnel  with  water.  Now 
close  the  upper  opening  of  the  fun- 
nel with  a  cork,  suck  out,  by  means 
of  a  glass  tube,  a  part  of  the  exterior 
water,  and  expose  the  vessel  to  the 
sun;  bubbles  of  air  will  soon  rise 
from  the  leaves,  and  collect  in  the  tube  of  the  funnel. 
When  the  water  is  so  far  pressed  down  within  the  fun- 
nel that  it  stands  on  a  level  with  the  exterior  water, 
then  uncork  the  funnel,  and  hold  a  glowing  shaving 
in  the  gas  evolved  from  the  leaves ;  the  shaving  will 
inflame  briskly,  just  as  it  would  in  oxygen  gas.  In- 
deed, this  gas  is  really  oxygen,  which  is  derived  from 
the  carbonic  acid  contained  in  the  water.  Thus,  in  the 
plants,  the  carbonic  acid  has  been  resolved  into  ita 
constituent  parts,  by  the  influence  of  light ;  its  oxygen 


GROWTH    OF    PLANTS.  617 

becomes  free,  and  escapes,  but  its  carbon  remains  be- 
hind in  the  plants.  The  plants  inhale  carbonic  acul> 
and  in  the  light  exhale  oxygen. 

Experiment.  —  Repeat  the  experiment,  but  with  this 
alteration,  —  p^our,  instead  of  common  water,  Selters 
water  over  the  leaves ;  this  contains  a  greater  abun- 
dance of  carbonic  acid,  and  the  consequence  is,  that 
the  evolution  of  oxygen  gas  proceeds  more  briskly,  and 
continues  longer. 

The*principal,  mass  of  plants  consists  of  vegetable 
tissue,  starch,  gum,  mucus,  sugar,  &c.,  each  composed 
of  three  elements  ;  all  these  may  be  produced  from  car- 
bonic acid  (C  CX)  and  water  (H  O),  when  the  elements 
of  the  water  combine  with  the  carbon  of  the  carbonic 
acid.  If  this  happens,  the  oxygen  of  the  latter  must 
necessarily  be  liberated.  From 

Carbonic   acid     =  Carbon,        Oxygen, 

and    Water          =    Hydrogen,   Oxygen, 

are    formed                Hydrogen,   Oxygen,   Carbon  -[-  Oxygen 
\^..  — v ^ 

Vegetable  tissue,  starch,  mucus,  sugar,  &c.        (is  liberated). 

It  is  also,  perhaps,  possible  that  the  elements  of  the 
carbonic  acid  combine  with  the  hydrogen  of  the  water, 
and  that  accordingly  the  oxygen  which  becomes  free  is 
derived  from  the  water ;  the  chemical  process  would 
then  be  different  from  that  just  stated,  but  the  results 
would  be  exactly  the  same.  From 

Water,  Hydrogen,      Oxygen, 

and  Carbonic  acid  =  Carbon,  Oxygen, 

are  formed                    Carbon,  Oxygen,  Hydrogen  -J-  Oxygen 
\ v i 

Vegetable  tissue,  starch,  mucus,  sugar,  &c.    (is  liberated) 

c.)  Ammonia  furnishes  plants  with  nitrogen.  —  When 
vegetable  and  animal  matters  decay,  ammonia  (N  HJ 
52* 


618  VEGETABLE    MATTER. 

is  formed  from  their  nitrogen,  carbonic  acid  from  theh 
carbon ;  both  of  these  products  combine  with  each 
other,  forming  a  volatile  salt  which  escapes  in  the  air. 
Jt  is  condensed  again  from  the  air,  partly  by  the  loam 
or  clay  (§256)  and  the  humus  of  the  soil  (§444),  partly 
by  the  dew,  rain,  and  snow,  and  returned  again  to  the 
earth,  and  then  with  the  water  absorbed  by  the  plants. 
If  organic  substances  decay  in  the  soil  where  plants  are 
growing,  the  ammoniacal  salt  is,  immediately  after  its 
formation,  absorbed  by  their  roots.  Whether  arAionia 
can  be  formed  directly  from  the  nitrogen  of  the  air, 
where  the  latter  is  in  contact  with  decaying  substances 
in  the  moist  earth,  and  can  be  of  service  to  the  plants, 
has  not  yet  been  ascertained  with  certainty ;  whereas  it 
may  be  regarded  as  proved  that  plants  have  the  power 
of  withdrawing  nitrogen  even  from  nitrates  when  these 
are  present  in  the  arable  soil. 

In  what  manner  the  assimilation  of  ammom^p  takes 
place  in  the  vegetable  kingdom  is,  indeed,  not  yet 
known,  but  it  is  probably  the  ammonia  from  which 
plants  take  the  nitrogen  requisite  for  the  formation  of 
their  azotized  constituents,  such  as  albumen,  gluten, 
caseine,  organic  bases,  &c.  From 

Carbonic  acid  =  Carbon,  Oxygen, 

Water  Hydrogen,  Oxygen, 

Ammonia       = Nitrogen,  Hydrogen, 

are  formed          Nitrogen,  Hydrogen,  Oxygen,  Carbon  -|-  Oxygen 

v ^ > 

Albumen,  gluten,  caseine,  organic  bases,  &c.         (is  liberated) 

Carbonic  acid,  water,  and  ammonia  accordingly  con- 
tain in  their  elements  the  essential  constituents  for 
the  formation  of  all  vegetable  substances  (carbon,  hy- 
drogen, oxygen,  and  nitrogen).  On  decay  and  putre- 
faction, animal  and  vegetable  matter  is  decomposed 
into  carbonic  acid,  water,  and  ammonia.  What  seema 


GROWTH    OF    PLANTS.  619 

to  us  to  be  annihilation  is,  however,  only  decay  ;  th** 
form  only  passes  away,  the  matter  itself  is  unchange- 
able. From  the  disgusting  substances  of  decay  are 
formed  again  the  living  wonders  of  the  vegetable  worli. 

Fig.  218. 


Dead  animals  and  plants.  Living  pid.au. 

d.)  Plants  are  furnished,  through  the  soil  and  water, 
with  the  requisite  inorganic  matters.  —  Our  arable  land 
is  constantly  undergoing  changes  ;  the  organic  matter 
contained  in  it  decays,  the  inorganic  is  decomposed  by 
the  action  of  time  and  weather.  By  the  last  process 
solubl^pialts  are  always  forming  from  insoluble  rocks, 
which  salts  may  now  be  absorbed  by  the  roots  of  plants. 
Weathering  takes  place  also  beneath  the  surface  of  the 
earth,  and  indeed  wTherever  air  and  water  can  pene- 
trate into  the  mass  of  rocks.  The  substances  thus 
rendered  soluble  are  taken  up  by  the  rain-water,  and 
constitute  the  salts  contained  in  our  common  spring 
and  river  waters ;  accordingly,  in  many  places  plants 
can  receive  from  water  also  inorganic  matter.  Finally, 
the  air  likewise  -contains  inorganic  substances  which 
have  been  conveyed  into  it  by  evaporation  (§  182), 
especially  from  the  ocean,  and  also  by  the.  force  of  the 
winds,  and  which  are  diffused  by  it  over  the  whole 
earth.  These  are  returned  again  to  the  earth  in  rain, 
dew,  snow,  &c.,  and  thus  we  can  no  longer  wonder  at 
finding  in  plants  salts  (for  instance,  common  salt)  not 
existing  in  the  rocks  from  which  the  soil  serving  as  a 
habitation  for  these  plants  has  been  formed.  The 


620  VEGETABLE    MATTER. 

changes  which  these  substances  undergo  in  living  plants 
have  already  been  noticed  in  the  preceding  section. 

It  should  still  be  expressly  stated,  that  a  plant  can 
grow  vigorously,  thrive,  and  attain  complete  maturity, 
only  when  the  substances  mentioned  at  a,  6,  c,  and  d 
are  all  four  presented  to  it  simultaneously.  As  the  life 
of  man  ceases  if  only  a  single  condition  necessary  for 
his  continued  existence  is  withdrawn,  for  instance,  the 
air  (oxygen),  or  water,  —  as  a  clock  stops  if  only  a 
single  wheel  is  taken  from  it,  —  so  also  the  complete 
development  of  a  plant  is  obstructed  when  One  of  the 
above-mentioned  means  of  nourishment  fails. 

CULTIVATED  PLANTS. 

615.  If  we  give  abundant  and  invigorating  food  to 
an  animal,  it  becomes  vigorous  and  fat;  on  scanty  and 
slightly    nourishing   food,    it   remains    poor   and    lean. 
Just  the  same  thing  occurs  also  with  plants J^When 
they  find  an  abundance   of  all   the   substances  which 
they  require  for  their  development  in  the  soil  and  in 
the  air,  they  will  grow  up  more  vigorously,  and   put 
forth   more  branches,  leaves,  flowers,  and  fruits,  than 
when  they  do  not  find  these  substances,  or  find  only  a 
part  of  them,  in  sufficient  quantity.     Consequently,  the 
way   of   obtaining   from  our  fields  and  meadows  the 
largest   produce    consists  in   presenting   to    the  plants 
which  are  to  be  cultivated  upon  them  all  the  materials 
requisite  for  their  nourishment   in  sufficient  quantity. 
We  do  this  by  manuring  the  soil. 

616.  Nature,  by  means  of  rain  and  dew,  decay  and 
putrefaction,  provides  that  the  three  universal  means  of 
nourishment,  water,  carbonic  acid,  and  ammonia,  shall 
not  be  wanting  to  plants ;  and  man  also,  without  exactly 
intending  it,  contributes  his  share  by  the  act  of  breath- 
ing and  by  the  fires  he  kindles.     The  air  contains  an  in- 


GROWTH    OF    PLANTS.  621 

exhaustible  provision  of  these  substances,  since  the  pro- 
cesses by  which  they  are  generated  on  the  earth  never 
suffer  an  intermission.  The  air  alone  would  accordingly 
suffice  for  the  nourishment  of  plants,  if  they  could  only 
find  in  the  soil  the  necessary  inorganic  salts  in  solution. 
But  as  a  structure  advances  more  rapidly  when  it  is 
worked  upon  at  several  parts  at  the  same  time,  so  the 
growth  of  a  plant  proceeds  more  rapidly  and  more  lux- 
uriantly when  it  can  take  up  nourishment  from  sev- 
eral different  sources,  not  only  by  the  leaves,  but  at  the 
same  time  also  by  the  roots.  All  vegetable  and  animal 
substances  are  converted  by  decay  into  water,  carbonic 
acid,  and  ammonia ;  hence  it  is  quite  natural  that  such 
substances,  when  they  decay  in  a  moist  soil,  should 
promote  the  growth  of  the  plants  sown  in  that  soil. 
Hereby  is  explained,  but  in  part  only,  the  beneficial  in- 
fluence exerted  upon  vegetation  by  the  universally  used 
animaljmd  vegetable  manures,  as,  for  instance,  the  so- 
called  humus-like  substances  formed  from  excrements, 
urine,  horn-shavings,  bone-dust,  guano,  straw,  leaves,  &c. 
617.  But  the  reception  of  these  universal  means  of 
nourishment,  and  their  transformation  into  organic  mat- 
ter by  the  vital  activity  of  the  plants,  can,  as  already 
mentioned,  only  take  place  by  the  aid  of  the  inorganic 
salts.  If  these  are  wanting  in  a  soil,  the  seeds  sown  in 
it  may  indeed  germinate  and  grow  for  a  while,  because 
they  contain  within  themselves  a  certain  quantity  of 
those  inorganic  constituents  which  the  plants  require 
for  their  growth,  but  the  growth  will  cease  when  the 
constituents  are  exhausted  in  the  development  of  the 
young  plants.  Nature  provides,  indeed,  for  the  forma- 
tion of  soluble  substances  in  the  earth,  by  the  gradual 
action  of  the  weather;  but  these  are  not  sufficient  to 
yield  a  rich  harvest  year  after  year  from  the  same  fields, 


622 


VEGETABLE    MATTER. 


and  it  is  therefore  indispensable  to  m.'x  these  constit- 
uents  artificially  with  the  soil  in  orc7^-  *o  maintain  its 
fertility.  This  is  done,  either  directly  by  those  mineral 
substances  which  contain  lime,  potassa,  soda,  phosphoric 
acid,  &c.,  as,  for  instance,  by  lime,  gypsum,  marl, 
wTood-ashes,  bone-ashes,  animal  charcoal,  common  salt, 
&c. ;  by  the  overflowing  of  meadows  with  water,  &c. ; 
or  indirectly,  by  the  salts  contained  in  most  kinds  of 
manure.  The  soluble  salts  existing  in  the  food  are  re- 
moved again  from  the  animal  body  by  the  urine  of  an- 
imals, the  insoluble  by  the  solid  excrements ;  and  thus 
is  explained,  in  a  simple  manner,  why  the  excrements 
of  animals  fed  upon  oats  are  the  most  appropriate  and 
most  powerful  manure  for  oats ;  those  of  animals  fed 
upon  peas,  clover,  or  potatoes,  the  best  manure  for  peas, 
clover,  or  potatoes.  In  these  saline  or  inorganic  sub- 
stances consists  the  second  mode  of  operation  of  the  an- 
imal and  vegetable  manures.  .  ^ 

Since  the  different  kinds  of  plants  require  different  in- 
organic substances,  and  different  quantities  of  them,  for 
their  nourishment,  —  some,  for  instance,  principally  salts 
of  potassa,  others  salts  of  lime,  and  others  again  phos- 
phates or  silicates,  —  so  it  is  advantageous  in  the  culti- 
vation of  plants  to  make  such  an  alternation  (rotation  of 
crops)  that  a  potassa  plant  shall  be  followed  by  a  lime 
plant,  and  this  again  by  a  silica  plant,  &c.  In  this 
way,  it  is  possible  to  obtain  from  a  field  which  is  ex- 
hausted for  one  kind  of  plant  a  second  or  a  third  crop 
consisting  of  a  different  species  of  plant,  without  the 
necessity  of  manuring  it  each  time. 

61rf.  It  is  clear  from  these  hints,  that  chemistry  alone 
can  give  to  the  farmer  a  knowledge  of  the  constituents 
of  his  soil,  of  the  constituents  of  the  plants  which  he 
wishes  to  cultivate  upon  this  soil,  and  of  the  substances 


RETROSPECT.  623 

which  must  be  added  to  it  in  order  that  the  plants  may 
find  there  all  that  is  necessary  for  their  nourishment. 
Inducement  enough  is  hereby  offered  to  every  fanner  to 
cultivate  a  more  intimate  acquaintance  with  this  sci- 
ence, as  the  only  guide  to  be  relied  upon  in  his  prac- 
tical experimehts  and  occupations. 


RETROSPECT  OF  VEGETABLE  MATTER 
IN  GENERAL. 

1.  WHILE  a  plant  lives,  a  constant  motion,  and  a 
constant  reception,  change,  and  surrendering  of  certain 
aeriform  and  liquid  substances,  are  continually  taking 
place  in  it.     If  these   substances   are  wanting  to  the 
plant,  its  growth  and  life  cease;  we  therefore  regard 
them  as  food  for  the  plant. 

2.  These  substances  all  belong  to  the  inorganic  com- 
pounds ;  they  consist,  — 

a.)  Of  a  combination  of  hydrogen  and  oxygen  (water). 

b.)  Of  a  combination  of  carbon  and  oxygen  (carbonic 
acid). 

c.)  Of  a  combination  of  nitrogen  and  hydrogen  (am- 
monia). 

d.)  Of  inorganic  acids  and  bases  (salts). 

3.  From  these  substances  are  formed,  in  an  incom- 
prehensible manner,  the  juices  of  the  plants,  and  from 
these  the  single  parts  of  the  plants  (organs),  together 
with  the  innumerable  vegetable  substances  which  we 
find  in  them. 

4.  The  vegetable  substances  may  be  classified  by  dif- 
ferent methods.     We  may  classify  them, — 

1.  According  to  their  more  or  less  general  diffusion :  — 


624  VEGETABLE    MATTER. 

a.)  Into  such  as  occur  in  almost  all  plants ;  for  in- 
stance, vegetable  tissue,  starch,  sugar,  gum,  mucus,  fats, 
many  acids,  chlorophyll,  albuminous  matter,  &c. 

b.)  Into  such  as  occur  only  in  certain  kinds  of  plants ; 
for  instance,  extractive  matter,  coloring  matter,  volatile 
oils,  resins,  many  acids,  organic  bases,  &c. 

II.  According  to  their  Jkemical  character :  — 
a.)  Into  vegetable  acids. 

b.)  Into  vegetable  bases. 

c.)  Into  indifferent  vegetable  matter. 

The  indifferent  combinations  predominate  in  the  veg- 
etable and  animal  kingdoms,  the  acids  and  bases  in  the 
mineral  kingdom. 

III.  According  to  their  composition :  — 

a.)  Into  non-azotized  substances,  and,  moreover, 

a.  into   those   rich   in    oxygen,    namely,    organic 

acids,  &c. ; 

ft.  into  those  rich  in  hydrogen,  namely,  fats,  vol- 
atile oils,  resins,  &c. ; 
y.  into  those   rich   in   carbon,  namely,  vegetable 

tissue,  starch,  sugar,  gum,  mucus,  &c. 
b.)  Into   azotized  substances;   for  instance,  organic 
bases,  many  of  the  coloring  matters,  &c. 

c.)  Into  those  containing-  nitrogen  and  sulphur;  for 
instance,  albumen,  gluten,  caseine,  &c. 

The  non-azotized  compounds  predominate  in  the 
vegetable  kingdom,  the  azotized  and  sulphurized  com- 
pounds in  the  animal  kingdom. 

5.  The  vegetable  substances  produced  by  nature  may 
be  transformed  and  decomposed  in  various  ways  into 
new  combinations.     They  may  be  changed,  — 
a.)  By  the  addition  of  oxygen;  as, 

a.  by  combustion  with  free  access  of  air  (carbonic 
acid,  water,  nitrogen)  ; 


RETROSPECT.  625 

/3.  by  decay  (humus,  carbonic  acid,  water,  ammo- 
nia, acidification  of  spirituous  liquids,  and  of  oth- 
er vegetable  substances ;  grass-bleaching,  &c.) ; 
y.  by  mere  exposure  to  the  air  (drying  or  becoming 
rancid  of  fats,  conversion  into  resin  of  the  vola- 
tile oils*,  &c.) ; 

5.  by   evaporation    (the   becoming   brown   of    ex- 
tracts, &c.) ; 

f.  by  the  action  of  nitric  acid,  chromic  acid,  and 
other  bodies  rich  in  oxygen  (conversion  of  sugar 
into  saccharic  acid,  oxalic  acid,  &c.). 
b.)  By  the  abstraction  of  oxygen  (reduction  of  indigo- 
blue). 

c.)  By  the  abstraction  of  hydrogen  (bleaching  with 
chlorine). 

d.)  By  combining'  with  sulphurous  acid  (bleaching  with 
this  acid. 

e.)  By  the  abstraction  of  hydrogen  and  oxygen  (trans- 
formation of  alcohol  into  ether  or  defiant  gas,  and  also 
of  oxalic  acid  into  carbonic  oxide  and  carbonic  acid 
by  sulphuric  acid ;  charring  of  wood  by  sulphuric  acid. 
&c.). 

/.)  By  the  addition  of  hydrogen  and  oxygen  (putre- 
faction of  vegetable  matter  with  exclusion  of  air,  as,  for 
instance,  under  water ;  that  is,  the  conversion  of  vege- 
table matter  into  carbonic  acid,  carburetted  hydrogen 
[marsh  gas],  water,  ammonia,  mud,  peat,  brown-coal, 
pit-c  al;  conversion  of  starch  or  sugar  into  lactic  acid, 
&c.) 

g.)  By  heating  with  exclusion  of  air  (charring  or  dry 
distillation  of  wood,  of  pit-coal,  of  the  fats,  of  the  acids, 
&c.,  that  is,  their  conversion  into  carbonic  acid,  car- 
hydrogen  [illuminating  gas],  water,  wood-vin- 
53 


626  VEGETABLE    MATTER. 

egar   [empyreumatic  acids],   ammonia,   tar  [burnt  oil, 
burnt  resin],  creosote,  wood-coal,  coke,  &c.). 

7t.)  By  the  peculiar  action,  not  yet  thoroughly  investi- 
gated, of  an  easily  decomposed  body  or  ferment  (spir- 
ituous fermentation,  that  is,  decomposition  of  sugar  into 
alcohol  and  carbonic  acid). 

i.)  By  the  transposition,  not  yet  explained,  of  one 
vegetable  substance  into  another  isomeric  (equally  con- 
stituted) compound;  for  example, — 

a.  conversion    of  starch  into  gum  and   sugar   by 

sulphuric  acid ; 
/3.  conversion    of  starch   into  gum  and  sugar   by 

diastase  ; 

y.  conversion  of  starch  into  gum  by  moderate  heat- 
ing; 
d.  conversion  of  crude  sugar  into  liquid  sugar  by 

heating  or  long  boiling  with  water ; 
€.  coagulation  of  albumen  by  heating,  &c. 
k.)  By  the  operation  of  strong-  bases  upon  vegetable 
matter ;  for  example,  — 

a.  formation  of  cyanogen  (§  291) ; 
/3.  formation  of  ammonia  (§  232) ; 
y.  formation  of  nitre  (§  207) ; 
d.  formation  of  soap  from  fats  (§  540). 
/.)  By  the  action  of  light  (formation  of  chlorophyll, 
bleaching  of  colors,  &c.). 

These  are  only  a  few  of  the  more  important  meta- 
morphoses of  vegetable  matter  as  yet  known  to  us; 
but  their  extent  is  unlimited,  and  increases  every  day, 
since  extraordinary  industry  and  zeal  are  now  devoted 
to  the  investigation  of  this  very  department  of  chem- 
istry. 


ANIMAL    MATTER. 


019.  THE  chemical  processes  which  take  place  in  the 
living  animal  are  far  more  mysterious  and  more  com- 
plex than  even  those  which  take  place  iti  plants.  That 
such  actions  really  do  occur  in  the  animal  body,  who 
can  doubt?  We  here  see  that  which  peculiarly  char- 
acterizes these  processes,  the  conversion  of  bodies  into 
new  bodies  with  entirely  new  properties,  far  more  dis- 
tinctly and  more  forcibly  than  in  plants  and  minerals 
For  can  there  be  a  more  striking  metamorphosis  than 
that  of  the  constituents  of  the  egg  (albumen,  yolk,  and 
egg-shell)  into  the  constituents  of  the  young  bird  (flesh, 
blood,  bones,  feathers,  &c.)  ?  or  the  conversion  of  milk, 
which  constitutes  the  sole  nourishment  of  many  young 
animals,  into  flesh,  blood,  &c.  ?  That  chemical  force 
alone  cannot  effect  these  changes  has  already  been 
stated  in  the  earlier  part  of  this  work ;  it  is  merely  the 
instrument,  the  means,  which  the  Divine  Power  has 
employed,  in  a  way  as  yet  concealed  from  us,  to  form, 
during  the  life  of  the  vegetables  and  animals,  all  the 
different  parts  of  the  vegetable  and  animal  kingdom. 
That  which  principally  distinguishes  animal  life  from 
vegetable  life  is,  that  during  the  former  oxygen  is  in- 
cessantly inhaled,  but  during  the  latter  it  is  exhaled; 
and  also,  that,  with  the  exception  of  water  and  some 


628  ANIMAL    MATTER. 

salts,  organic  substances  only  are  appropriated  to  the 
support  of  the  former. 

620.  The  chief  mass  of  vegetable  matter  consists  of 
non-azotized    substances,   consequently    of    substances 
which  contain  only  three  elements ;  but  in  the  animal 
body,  on  the  contrary,  the   azotized    and   sulphurized 
substances    (albuminous  substances),    consequently  far 
more  complex  combinations,  predominate.     Water  and 
fat  are  almost  the  only  substances,   composed   of  only 
two  or  three  elements,  that  occur  in  the  animal  body ; 
all  the  others,  for  instance,  flesh,  cartilage,  blood,  hair, 
nails,  &c.,  are  rich   in  nitrogen,   sulphur,   and  also  in 
phosphorus.     It  is  also  characteristic  of  these  substan- 
ces that  they  do  not  assi  ne  a  crystalline  form ;  we  find 
crystalline   combination    —  as,   for   instance,    in    urine 
(urea,  uric  acid,  &c.)  -    in  those  animal  liquids  only, 
which,  being  unfit  for  assimilation,  are  again  separated 
from  the  body.     Most  animal  substances,  when  viewed 
under  the  microscope,  exhibit  the   form  of  small  glob- 
ules.     Accordingly,  the  globular   form    is    the    funda- 
mental form  for  the  composite,  more  highly  organized 
types  of  the  animal  kingdom,  while  in  the  more  simple, 
lifeless  productions  of  the  mineral  kingdom,  the  angu- 
lar form  (crystalline  form)  prevails.     In  the  vegetable 
kingdom,  holding  a  middle  position  between  the  two, 
we  find  both  forms,  namely,  the  globular  or  spherical 
in  starch,  yeast,  &c. ;  the  crystalline  in  sugar,  in  organic 
acids,  bases,  &c. 

621.  The  elementary  matter  from  which  the  proxi- 
mate constituents,  and  from  which  again  the  organs  of 
the  animal  body,  are  formed,  is  exactly  the  same  as 
that  which  occurs  in  the  vegetable  kingdom,  namely, 
oxygen,  hydrogen,  carbon,  nitrogen,  *  dphur,  phosphorus, 
and  chlorine  /  and  the  metallic  subs  ;ances,  lime,  polas* 


THE    EGG. 


629 


«ww,  sodium,  and  iron.  These  must  be  introduced  into 
the  animal  body  in  order  that,  it  may  grow  and  live. 
How  this  happens  may  be  shown  most  simply  in  the 
constitution  of  the  egg  and  of  milk. 


I.    THE  EGG. 

The  egg,  as  is  known,  consists  of  the  albumen,  the 
yolk,  and  the  shell. 

622.  Albumen.  —  The  ivhite  in  the  hen's  egg  consists 
of  cells,  in  which  is  contained  a  coforless  alkaline  liquid, 
the  albumen.     On   evaporation,  we  obtain  from  it  one 
eighth    of  solid   albumen ;   the  rest  is  water.     When 
burnt,  it  leaves  behind  common  salt,  carbonate,  phos- 
phate, and   sulphate   of  soda,  and  phosphate  of  lime. 
That  albumen,  when  briskly  beaten  up,  yields  a  po- 
lous  light  froth,  that  it  becomes  insoluble  and  coagu* 
Jates   by  heating,  &c.,  are  well  known  facts.     On  ac- 
count of  the  latter  property,  it  is  used  for  clarifying 
turbid  liquids,  especially  the  juices  of  sugar. 

Experiment.  —  Stir  up  some  honey  in  warm  water, 
add  a  little  albumen  to  the  turbid  solution  obtained, 
and  heat  the  mixture  to  boiling.  The  albumen  seizes 
upon  the  foreign  substances  floating  in  the  liquid,  bears 
them  to  the  surface,  and  incloses  them  within  itself  as 
it  coagulates;  the  liquid  thereby  becomes  clear  and 
transparent,  and  may  be  separated  by  a  strainer  from 
the  coagulated  albumen. 

The  constituents  of  animal  albumen  are  just  the 
saire  as  those  of  vegetable  albumen  (§  477). 

623.  The  yolk  of  fgg's  consists  of  albumen  holding 
in  suspension  yellow  drops  of  oil.     On  account  of  the 
albumen  contained   in  it,  it  coagulates  when   heated, 
and  the  fat  (oil  of  yolk  of  eggs)  may  be  extracted  from 

53* 


630  ANIMAL    MATTER. 

it  by  strong  pressure,  or  by  agitation  with  ether.  Phos- 
phorus is  contained  in  the  oil  of  yolk  of  eggs. 

624.  Egg-shells.  —  Experiment.  —  Pour  some  diluted 
muriatic  acid  upon  some  egg-shells ;  with  the  exception 
of  some  membrane,  they  will  entirely  dissolve,  with  the 
evolution  of  gas.  The  gas  which  escapes  is  carbonic 
acid ;  but  lime  is  contained  in  solution  in  the  muriatic 
acid,  as  we  may  ascertain  by  the  addition  of  sulphuric 
acid,  which  throws  down  gypsum  from  it.  The  shells 
have  accordingly  the  same  constitution  as  chalk,  name- 
ly, they  consist  of  carbonate  of  lime. 

There  are  in  the  egg-shells  small  pores,  through 
which  the  air  penetrates  into  the  interior  of  the  egg, 
and  gradually  effects  a  change  (putrefaction)  of  the 
latter.  If  these  openings  are  stopped  up,  —  for  in- 
stance, by  packing  the  eggs  in  ashes,  or  by  smear- 
ing them  with  oil,  —  the  eggs  will  keep  much  longer 
unchanged,  as  the  penetration  of  the  air  is  thus  pre- 
vented. 

H.    MILK. 

Milk  consists  of  a  solution  of  caserne  and  sugar  of 
milk  in  water,  in  which  solution  small  globules  of  oil 
are  held  suspended.  The  latter  render  the  milk  opaque, 
and  give  it  the  appearance  of  an  emulsion. 
•625.  The  Oil- Globules.  —  Experiment. —  These  glob- 
ules cannot  be  separated  from  the  milk  by  filtration 
alone,  as  they  are  so  small  that  they  pass  with  it 
through  the  pores  of  the  finest  paper;  but  it  may  be 
accomplished  in  the  following  manner.  Dissolve  an 
ounce  of  Glauber  salts  and  a  couple  of  grains  of  carbon- 
ate of  soda  in  half  an  ounce  of  lukewarm  water,  and 
agitate  the  solution  with  half  an  ounce  of  fresh  milk. 


MILK.  63\ 

If  you  now  transfer  this  mixture  to  a  fiHer,  the  fatty 
portions  (cream)  remain  behind,  while  a  liquid,  only 
slightly  opalescent,  passes  through.  The  saline  solu- 
tion added  does  not  act  chemically  upon  the  constitu- 
ents of  the  milk,  but  it  only  acts  mechanically,  causing 
the  globules  to  form  a  more  compact  mass,  and  to  be 
more  readily  separated  from  the  watery  liquid. 

626.  Ca seine.  —  Experiment.  —  If  you    add  to   the 
filtered  liquid  a  few  drops  of  muriatic  acid,  the  caseine 
separates  from  it  as  a  white  flaky  mass ;  accordingly, 
the  animal  caseine  is  likewise  coagulated  and  rendered 
insoluble  by  acids  in  the  same  manner  as  vegetable 
caseine  (§  452),  with  which  it  exactly  agrees  in  consti- 
tution.    Pure  caseine  is  insoluble  in  water,  but  it  dis- 
solves in  it  when  alkalies  are  present ;    these   always 
exist  in  the  milk,  and  keep  the  caseine  in  solution.     The 
alkali    (soda)    is  withdrawn   from  the  caseine  by  the 
acids  which  are  added,  and  the  caseine  then  separates 
in    the   familiar   form  of  new  cheese.     Caseine  is  an 
albuminous  substance,  that  is,  it  contains,  besides  car- 
bon, hydrogen,  and  oxygen,  also  some  nitrogen  and  sul- 
phur in  its  constitution. 

627.  Albumen.  —  Experiment.  —  If  you  filter  the  ca- 
seine from  the  liquid,  and  then  boil  the  latter,  it  again 
becomes  turbid,  although  less  so  than  before.     It  is  the 
albumen  which  separates,  small  quantities  of  it  being 
present  in  all  milk. 

628.  Experiment.  —  Let  a  small  piece  of  the  dried 
membrane  of  the  stomach  of  a  calf  (rennet)  remain 
standing  one  night  in  a  spoonful  of  water,  and  after- 
wards pour  this  water  upon  a  quart  of  new  milk ;  the 
milk,  after  having  stood  for  some  hours   in   a  warm 
place,  will  coagulate  into  a  gelatinous  mass,  which  is 
to  be  put  upon  a  filter.     What  remains  behind  consists 


632  ANIMAL    MATTER. 

of  an  intimate  mixture  of  the  curdled  caseins  with  glob- 
ules of  fat.  By  pressing  and  drying,  we  obtain  from  it 
the  so-called  cream  or  new-milk  cheese  (Swiss,  Dutch, 
Chester,  &c.  cheese). 

629.  Sugar  of  Milk.  —  Experiment.  —  Separate  the 
filtered  liquid  (sweet  whey)  from  its  albumen  by  boil- 
ing, and,  having  again  filtered  it,  evaporate  till  only  a 
few  ounces    of  it   remain.      If  left  in  a  warm  place, 
hard,  prismatic  white  crystals  of  sugar  of  milk  will  be 
deposited   (§  473).      By  this  method  sugar  of  milk  is 
procured  in  Switzerland  on  a  large  scale.     Consequently 
the  sweet  whey  is  to  be  regarded  principally  as  a  solu- 
tion of  sugar  of  milk  (together  with  some  albumen  and 
some  salts)  in  water. 

Experiment.  —  Dissolve  again  in  water  the  sugar  of 
milk  obtained,  and  put  a  piece  of  rennet  in  the  solu- 
tion ;  the  liquid  will  soon  become  sour  in  a  warm 
place,  because  the  sugar  of  milk  is  converted  into 
lactic  acid. 

630.  Experiment.  —  The  coagulation   of  the   milk, 
which  was  produced  by  the  rennet  in  a  few  hours,  is 
effected  instantaneously  by  the  addition  of  acids,  as  is 
rendered  obvious  by  adding  a  few  drops  of  some  acid  to 
heated  milk.    In  this  curdled  mass  are  contained  all  the 
caseine  and  fatty  particles  of  the  milk  (cheese  and  butter). 

631.  Experiment.  —  Fill  a  flask  with  fresh  milk,  close 
it,   and  keep  it,  inverted,   from  twenty-four  to   thirty- 
six  hours  in  a  cool  place ;  then  loosen  the  stopper  a 
little,  so  that  the  lower,  thinner  portion  of  the  milk  (blue 
or  skim  milk)  may  run  off,  but  the  upper,  thicker  part 
(cream)  remain  behind.     On  standing,  the  lighter  oil- 
globules  of  the  milk  ascend,  and  form  on  the  surface  the 
well-known  fatty,  thick  cream.     If  this  is  shaken  for 

time,  the  membranes  of  the  oil-globules  are  torn, 


MILK.  633 

and  the  latter  then  unite  together,  forming  masses  of 
butter.  The  thin  milk  which  passes  off  from  beneath 
may  be  separated,  in  the  way  already  described,  into 
caseine  albumen,  and  sugar  of  milk. 

Butter,  like  the  vegetable  fats,  consists  of  a  solid  fat 
(margarine)  *and  a  fluid  (oleine),  and  it  has  also  exactly 
the  same  properties  (§  533).  But  besides  these  two 
kinds  of  fat,  butter  contains  a  small  quantity  of  a  pe- 
culiar fat  (butyrlne).  If  butter  remains  exposed  some 
time  to  the  air,  some  volatile  fat  acids  having  a  dis- 
agreeable smell  and  taste  will  be  generated  in  it ; 
these  cause  the  rancidity  of  butter.  If  butter  that  has 
become  rancid  is  boiled  several  times  with  double  its 
quantity  of  water,  these  acids  will  be  removed  from  it, 
and  the  butter,  on  cooling,  will  have  regained  its  agree- 
able flavor. 

632.  If  you  let  milk  stand  for  some  time  in  open  ves- 
sels, its  sugar  of  milk  is  gradually  converted  into  lactic 
add,  and  this,  like  every  other  acid,  causes  a  curdling 
of  the  milk,  and  at  the  same  time  its  well-known  sour 
taste.  But  the  curdling  first  commences  after  most  of 
the  oil-globules  have  collected  on  the  surface  (sour 
cream).  From  this  cream  butter  is  most  usually  pre- 
pared with  us,  and  therefore  the  buttermilk  remaining 
(a  mixture  of  curdled  caseine,  lactic  acid,  and  water, 
with  some  particles  of  butter  remaining  behind)  has  an 
acid  taste.  The  so-called  curd  beneath  the  cream  con- 
tains only  some  traces  of  fat,  and  consists  accordingly 
of  water,  lactic  acid,  and  coagulated  caseine.  By  press- 
ing we  obtain  from  it  the  sour  whey,  and,  as  a  residuum, 
i he  coagulated  caseine,  from  which  our  common  skim- 
wilk  cheese  is  made.  When  kept  damp  this  under- 
goes a  decomposition  (putrefaction),  by  which  ammo- 
nia is  generated,  which  forms  with  the  caseine  a  soft 


634  ANIMAL    MATTER. 

saponaceous  mass.  If  the  putrefaction  advances  still 
farther,  there  will  be  finally  generated  also  volatile  com- 
pounds of  a  very  offensive  odor  (sulphuretted  hydrogen, 
volatile  fat  acids,  &c.). 

633.  Fermentation  of  Milk.  —  Experiment.  —  Let  milk 
stand  in  a  flask  till  it  begins  to  curdle,  and  then  put  the 
flask  furnished  with  a  tube  for  the   evolution  of  gas 
(Fig.  188)  in  a  place  the  temperature  of  which  ranges 
from  24°  to  30°   C.      A  brisk  evolution  of  carbonic 
acid  will  commence,  because  the  sugar  of  milk,  which 
has  not  yet  passed  into  lactic  acid,  is  converted,  at  a 
higher  temperature,  first  into  grape,  sugar,  and  then  into 
alcohol  and  carbonic  acid.     But  there  is  also  formed 
at  the  same  time  some  butyric  acid,  which  imparts  a 
disagreeable  taste  to  the  spirit,  obtained  by  the  distilla- 
tion of  the  fermented  liquid  after  it  has  been  strained 
and  squeezed  off.      The  koumiss  prepared  by  the   Cal- 
mucs  is  a  liquor  obtained  by  the  fermentation  of  mare's 
milk. 

634.  Ashes  of  Milk.  —  If  milk  is  burnt  with  access 
of  air,  there  remain  behind,  after  all  its  carbon,  hydro- 
gen, oxygen,   and   nitrogen  have  been  converted  into 
aeriform  combination,  ashes,  which  consist  of  potassa, 
soda,  lime,  magnesia,  and  sesquioxide  of  iron,  and  also 
of  phosphoric  acid,  sulphuric  acid,  and  chlorine. 

635.  Digestion.  —  If  we  reconsider  the  constituents 
of  the  egg  and  the  milk,  as  just  stated,  we  find  in  them 
1he  following  elementary  substances  :  — 

The  egg  consists  of  Milk  consists  of 

Water         =  H,  0.  Water  =  H,  O. 

Oil  of  eggs  =  H,  0,  C,  P.  Butter  )  _  _  n  _ 

Albumen     =  H,  0,  C,  N,  S,  P.         Sugar  of  milk  \  ~ 

Caseine     >          = 
Albumen  $ 

Shells  and  other  in-  >  Ca,  Na,  K,  Fe,  Inorganic  sub-  >  =Ca,Na,K,Mg,Fe, 
organic  substances  }  P,  S,  01,  O.  stances  5       P,  S,  Cl,  O. 


MILK,  G35 

But  exactly  the  same,  and  only  the  same,  elementary 
substances  are  found  also  in  the  animal  body ;  accord- 
ingly, it  must  be  concluded  that  the  constituents  of  the 
hen's  egg  are  used,  in  the  hatching  of  the  egg,  for  the 
development  of  the  young  chicken,  and  the  constituents 
of  the  milk  which  forms  the  food  of  the  young  Mam- 
malia are  used  for  the  growth  and  nourishment  of  the 
latter.  It  is  the  same,  also,  with  the  constituents  of 
the  vegetable  and  animal  substances,  which  serve  us  as 
food.  The  food  is  mixed  up  in  the  stomach  with  the 
gastric  juice  (a  liquid  containing  free  muriatic  acid  and 
common  salt,  which  liquid  is  secreted  by  the  inner  skin 
of  the  stomach,  -^mucous  membrane),  and  is  thereby 
softened  into  a  soluble,  white,  pulpy  mass  (chyme). 
The  muriatic  acid  is  likewise  formed  by  a  decomposi- 
tion of  common  salt  taking  place  in  the  body,  and  it  is 
indispensable  for  the  solution  (digestion)  of  the  food. 
The  explanation  of  this  action  is,  that  water,  rendered 
feebly  acid  by  muriatic  acid,  is  able  (after  it  has  been 
previously  left  in  contact  for  a  day  with  a  piece  of 
rennet)  to  dissolve,  at  a  temperature  of  from  3(P  to 
40°  C.,  hard-boiled  albumen,  flesh,  and  other  food.  All 
of  the  chyme  which  has  become  soluble  is,  during  its 
passage  through  the  intestines,  absorbed  and  introduced 
as  nourishment  (chyle)  into  the  blood.  The  changes 
which  the  food  experiences  in  the  animal  body  are  there- 
fore the  following :  from  the  food  is  formed  chyme, 
from  this  chyle,  from  this  blood,  and  from  the  blood  all 
the  numerous  organs  and  parts  of  the  animal  body  are 
generated,  just  as  all  the  organs  and  parts  of  plants  sure 
generated  from  the  vegetable  juices. 


636  ANIMAL    MATTER. 


in.    THE  BLOOD. 

Like  milk,  the  blood  also  consists  of  a  liquid  as  clear 
as  water,  in  which  small  globules  are  held  suspended ; 
but  these  globules  (blood  corpuscles)  have,  however,  a 
yellowish-red  color. 

636.  Experiment.  —  If  you  let  the  blood  of  an  animal 
remain  standing  quietly  in  a  vessel,  it  will,  in  a  short 
time,  undergo  a  change  ;  it  coagulates,  forming  a  dark- 
red  jelly  (the  dot,  coagulum),  which  contracts  on  longer 
standing,  and  a  yellowish-liquid  is  separated  (serum). 
When  the  latter  is  heated  to  boiling,  it  coagulates  to  a 
white  jelly  ;  the  serum  consists  of  a  solution  of  albumen. 
There  are  two  substances  combined  together  in  the 
coagulum,  one  of  which  dissolves  by  long  washing  in, 
water,  communicating  to  it  a  red  color  (coloring'  matter 
of  the  blood,  the  principal  constituent  of  the  blood  cor- 
puscles), while  the  other  remains  behind  as  a  white 
fibrous  mass  (animal  fibrine).  Accordingly,  the  most 
important  proximate  constituents  of  the  blood  are 
water,  albumen,  blood  corpuscles,  and  animal  fibrine, 
which,  on  the  standing  of  the  blood,  are  transposed  in 
the  following  manner :  — 

From         Water,  Albumen,  Blood  Corpuscles,  Fibrine, 


are  formed        Serum  and  Coagulum. 

It  is  a  distinguishing  peculiarity  of  the  coloring  mat- 
ter of  the  blood,  that  it  always  contains  iron. 

637.  Experiment.  —  If  the  blood  freshly  drawn  from 
the  veins  is  beaten  up  during  cooling,  it  does  not 
coagulate ;  the  fibrine  is  indeed  insoluble,  and  exists 
as  a  thread-like  coherent  mass,  which,  when  knead- 
ed for  some  time  with  water,  becomes  finally  white, 
and,  after  drying,  resembles  the  muscular  fibre.  In- 


THE    BLOOD.  637 

deed,  it  may  be  regarded  as  half-formed  flesh,  since  it 
has  entirely  the  same  composition,  and  the  flesh  of  the 
animal  body  is  formed  from  it.  The  blood  remaining 
behind  retains,  after  the  separation  of  the  fibrine,  its  red 
color,  and  coagulates  on  boiling  to  a  jelly  of  a  dark- 
red  color,  a&  may  be  perceived  in  the  so-called  black- 
pudding*  The  metamorphosis  of  the  blood  just  treated 
of  is,  accordingly,  as  follows  :  — 

Water,  Albumen,  Blood  Corpuscles  Fibrine 

remain  liquid.  becomes  solid. 

Fibrine  belongs  to  the  albuminous  substances ;  it  is 
very  rich  in  oxygen,  and  contains  also  sulphur  and 
phosphorus  in  organic  combination. 

638.  The  Ashes  of  Blood.  —  If  blood  is  evaporated  to 
dry  ness,  and  heated  for  a  long  time  in  the  air,  it  will 
finally  burn  up,  with   the   exception    of   some    ashes. 
These  ashes  consist  of  alkaline  phosphates  (much  soda, 
little  potassa),  phosphates  of  the  alkaline  earths  (lime, 
magnesia),  phosphate  of  the  sesquioxide  of  iron,  com- 
mon salt,  and  the  alkaline  sulphates ;  consequently,  of 
the  same  constituents  which  we  find  in  the  ashes  of  our 
principal  articles  of  nourishment  (eggs,  milk,  bread,  &c.). 
In  the  vegetable  kingdom  we  find  these  ash-constituents 
most  abundant  in  those  vegetable  parts  which  are  rich 
in  albuminous  matter,  especially  in  the  seeds  of  our 
grains  and  leguminous  plants. 

639.  Respiration  and  Means  of  Nourishment.  —  As 
long  as  an  animal  lives,  its  blood  is  in  a  state  of  con- 
stant motion  and  of  constant  change.      Light-red  blood 
streams  out  from  the  heart,  through  the  arteries,  i  .to  all 

*  "  Mixed  with  fats  and  aromatics,  and  inclosed  in  the  prepared  intes- 
tines, the  blood  of  this  animal  [the  pig]  constitutes  the  sausages  sold  in  the 
shops  under  the  name  of  black-puddinys"  —  Pereira  on  Food  and  Diet. 

54 


638  ANIMAL    MATTKR. 

parts  of  the  body,  from  which  it  returns,  darker  colored, 
through  the  veins,  back  again  to  the  heart.  But  before 
the  latter  blood  recommences  its  circulation,  it  is  im- 
pelled through  the  lungs,  in  which  it  comes  in  imme- 
diate contact  with  the  inhaled  air,  and  by  means  of 
which  it  experiences  a  most  remarkable  change.  When 
in  contact  with  the  air,  the  dark  venous  blood  is  con- 
verted again  into  light-red  arterial  blood,  and  thereby 
the  air  loses  a  part  of  its  free  oxygen,  and  receives  in 
return  carbonic  acid  and  vapor ;  the  exhaled  air  is  ac- 
cordingly poor  in  oxygen,  but  rich  in  carbonic  acid  and 
vapor.  This  change  of  the  air  is  obviously  very  much 
like  that  which  the  air  undergoes  by  the  process  of  com- 
bustion ;  for  in  this  case,  too,  its  free  oxygen  is  convert- 
ed into  carbonic  acid  and  water.  Indeed,  this  similarity 
is  rendered  still  more  apparent,  when  we  consider,  more- 
over, that  heat  becomes  free  also  in  the  animal  body,  as 
long  as  it  lives  and  breathes,  and  that  the  food  received 
into  it,  like  wood  in  the  stove,  entirely  disappears,  with 
the  exception  of  a  small  portion  which  passes  off  in  the 
form  of  excrements.  Its  disappearance  takes  place  in 
exactly  the  same  way  as  that  of  wood,  with  which  we 
heat  our  apartments ;  this  disappearance  is  caused  by 
a  change  of  the  food  into  aeriform  combinations,  into 
carbonic  acid  and  vapor,  which  are  partly  exhaled  by 
the  lungs,  and  partly  evaporated  from  the  skin. 

For  this  purpose,  as  it  seems,  non-azotized  food, 
namely,  starch,  sugar,  gum,  fat,  lactic  acid,  and  other 
organic  acids,  beer,  wine,  &c.,  are  principally  employed, 
and  are  therefore  called  elements  of  respiration. 

It  is  different  with  those  substances  which  contain 
nitrogen,  sulphur,  and  phosphorus;  these  serve  for 
the  production  of  blood,  the  constituents  of  which  are 
the  same.  These  substances,  albumen,  fibrine,  &c., 


THE    FLESH. 


639 


afterwards  pass  with  the  blood  into  all  parts  of  the 
animal  body,  and  are  transformed  into  flesh,  nerves, 
muscle,  hair,  nails,  &c.  For  this  reason,  they  have 
been  called  the  plastic  elements  of  nutrition.  Those 
azotized,  sulphurized,  and  other  substances,  such  as 
salts,  which  can  no  longer  be  used  in  the  animal  body, 
are  removed  from  it  again  by  the  solid  excrements  and 
the  urine. 


IV.    THE   FLESH. 

What  is  commonly  called  meat  (muscle)  is  likewise 
(see  §  637)  animal  fibrine  or  muscular  fibre.  In  this 
form  it  consists  of  bundles  of  fine  fibres,  which  are  in- 
terwoven with  cellular  tissue,  nerves,  and  veins,  and  are 
thoroughly  penetrated  with  a  watery  liquid,  the  so- 
called  juice  of  flesh. 

640.  Juice  of  Flesh.  —  Experiment.  —  Mince  a  quar- 
ter of  a  pound  of  lean  meat  very  fine,  pour  over  it  a 
quarter  of  a  pound  of  water,  and,  after  letting  it  stand 
fifteen  minutes,  press  out  the  liquid  through  a  linen 
cloth ;  pour  over  the  residue  the  same  quantity  of  wa- 
ter, squeeze  out  the  liquid,  and  mix  this  with  the  former 
liquid.  In  the  reddish  juice  are  contained  almost  all 
the  soluble,  and,  at  the  same  time,  all  the  savory  and 
odorous  constituents  of  the  flesh.  If  this  juice  is  heated 
to  60°  C.,  a  frothy  mass  separates  from  it,  which  con- 
sists of  coagulated  albumen.  When  the  liquid  filtered 
off  from  this  is  boiled  for  some  time,  a  turbidness  again 
ensues,  which  is  caused  by  the  coloring1  matter  and 
fibrine  (§636)  of  the  blood  extracted  also  from  the  flesh, 
which  likewise  coagulate  at  a  boiling  heat.  The  acid 
oroth  or  decoction  (bouillon)  now  remaining  behind 
contains  free  phosphoric  and  lactic  acids,  phosphate  and 


640 


ANIMAL    MATTER. 


.actate  of  the  alkalies  (much  potassa,  little  soda),  phos- 
phate of  magnesia,  together  with  several  organic  mat- 
ters, a  crystalline,  indifferent  organic  body  (creatine)j 
and  a  crystalline,  basic,  organic  body  (creatinine),  nei- 
ther of  which  has  been  yet  thoroughly  investigated. 
By  evaporation  the  broth  becomes  yellow,  and  finally 
brown  (roast-broth) ;  if  evaporated  to  dryness,  a  dark- 
brown  soft  mass  (extract  of  flesh)  remains  behind,  half 
an  ounce  of  which  is  sufficient  to  convert  one  pound  of 
water,  to  which  some  common  salt  has  been  added, 
into  a  strong  and  savory  soup. 

641.  Fibrous  Tissue.  —  Experiment.  —  If  you  boil  the 
fleshy  residue  left   after  the   former  experiment  with 
water  for  some  hours,  you  obtain  a  liquid  which  coag- 
ulates in  the  cold  to  a  jelly,  and  consists  principally  of 
a  solution  of  gelatine  ;  the  fat  floating  on  the  surface 
proceeds  from  the  tallow,  or  fat  of  the  flesh.     What  re- 
mains is  fibrous  tissue,  a  milk-white,  hard,  tasteless,  and 
odorless  fibrous  mass  ;  in  this  hardened  state  it  is  diiii- 
cultly  digestible,  and  but  slightly  nutritious. 

The  annexed  grouping  gives  a  probable  idea  of  the 
quantitative  composition  of  the  flesh.  From  one  thou- 
sand pounds  of  beef  were  obtained,  — 

a.)  By  expression   with   water   (consisting 

one  half  of  albumen),           ...  60  Ibs. 
b.)  By  five  hours'  boiling  with  water  (con- 
sisting chiefly  of  gelatine),       .  6  " 
c.)  Lean,  juiceless,  and  tasteless  fibrine,        .  •  164  " 

d.)  Fat  or  tallow, 20  " 

e.)   Water, 750  " 

loOO  Ibs 

642.  Boiling1  of  Meat.  —  To  obtain  by  boiling  an  ex- 
rellently  tender,  savory,  and  nutritious  meat,  care  must 


THE    FLESH.  641 

be  taken  that  the  juice  is  not  extracted  from  the  flesh 
during  boiling,  but  remains  in  it,  and  that  the  boiling 
is  not  continued  too  long.  If  the  albumen  contained  in 
the  juice  remains  in  the  interstices  of  the  animal  fibres, 
a  tender  roasted  or  boiled  meat  is  obtained  ;  but  if, 
during  the  boiling^or  roasting,  the  juice  goes  into  the 
broth  or  gravy,  then  the  meat  becomes  tough  and  hard. 
It  is  best  to  put  the  meat  to  be  boiled  into  boiling  wa- 
ter, continue  the  boiling  for  several  minutes,  and  then 
let  it  stand  for  some  hours  in  the  kettle  on  the  hearth 
of  the  stove,  where  the  temperature  is  about  70°  C. 
In  this  way  the  albumen  in  the  external  layers  of  the 
meat  is  immediately  coagulated  by  the  boiling  water, 
and  forms,  in  this  coagulated  state,  a  coating  which 
prevents  the  escape  of  the  liquid,  and  likewise  the  pen- 
etration of  the  external  water  into  the  interior  of  the 
meat. 

643.  Preparation  of  Broth,  or  Soup.  —  We  must  man- 
age in  just  the  contrary  way  if  we  wish  to  obtain  a 
good  and  abundant  soup  from  the  meat.  To  effect 
this,  rnince  the  meat  fine,  mix  it  uniformly  with  an 
equal  weight  of  cold  water,  heat  it  slowly  to  ebullition, 
let  it  boil  for  a  few  minutes,  and  finally  strain  off  and 
squeeze  out  the  liquid.  By  adding  to  this  liquor  some 
common  salt,  and  other  ingredients  with  which  soups 
are  commonly  seasoned,  and  then  coloring  it  somewhat 
darker  with  onions  burnt  brown,  or  with  burnt  sugar, 
to  give  it  the  ordinary  favorite  brownish  color,  we  ob- 
tain the  best  soup  which  can,  in  general,  be  prepared 
from  a  given  quantity  of  meat.  Hitherto,  it  has  been 
frequently  assumed  that  gelatine  formed  the  most  im- 
portant, most  characteristic  constituent  of  animal  soup  , 
but  this  is  a  mistake,  since  the  gelatine  itself  is  quite 
tasteless,  and  forms  but  a  very  insignificant  part  of  the 
54* 


642  ANIMAL    MATTER. 

soup.  And  for  this  reason,  the  so-called  portable  soup 
prepared  in  England  and  France  cannot  yield  a  really 
good  animal  broth. 

644.  Salting  of  Meal.  —  A  universally  known  method 
of  preserving  meat  is  to  salt  it  down,  that  is,  to  rub  into 
it  and   strew   over  it  some   common   salt,   and   let  it 
remain   piled  up,  or   pressed  together,  for  some  time. 
The  common  salt  extracts  from  the  flesh  one  third  to 
one  half  of  the  juice,  dissolves  in  it,  and  forms  with 
it  the  so-called  brine.     Since,  consequently,  a  large  por- 
tion of  the  nutritive  albumen,  and  of  the  lactates  and 
phosphates  essential  to  digestion  and  nourishment,  and 
also  of  the  creatine  and  creatinine,  are  removed  with 
this  brine  from  the  meat,  the  latter  must  lose  in  nutri- 
ture,  and  it  is  not  improbable  that  this  is  the  reason 
why  a  long  continued  dieting  on  salt  meat — for  in- 
stance, during  sea-voyages  —  is  followed  by  scurvy  and 
other  maladies.     Hence,  it  would  be  better  not  to  let 
the  salting  of  the  meat  continue  till  a  brine  is  formed. 

V.   THE  BILE. 

645.  The  bile  separates  in  the  liver  from  the  venous 
blood  ;  it  consists  of  a  thickish,  greenish-yellow  liquid, 
and  possesses  a  very  bitter  taste.     Its  chief  constituents 
are  choleic  acid  and  soda,  which,  combined  with  each 
other,  have  a  saponaceous  character.     If  you  shake  up 
bile  with  water  the  solution  froths  like  soap-suds ;  it 
also  comports  itself  like  this  towards  greasy  substances, 
and   therefore   is    frequently   used    for    washing   silks, 
which,  by  the  application   of  soap,  would  lose  their 
color.     The  dried  gall-bladder  of  the  carp  forms  an  ar- 
ticle of  commerce. 

Experiment.  —  Dissolve  a  little   carp-gall,   or   some 


THE    SKIN.  643 

drops  of  fresh  ox-gall,  in  a  little  water,  and  add  grad 
ually  to  the  solution  sufficient  common  sulphuric  ack1 
entirely  to  redissolve  the  precipitate  formed  ;  if  you  now 
add  a  few  drops  of  sugared  water,  or  thin  starch-paste, 
the  liquid,  .unless  rendered  too  hot  by  the  addition  of 
sulphuric  acid,  assumes  a  splendid  violet-color.  In  this 
way,  extremely  small  quantities  of  sugar  or  starch,  or, 
inversely,  of  bile,  may  be  detected. 

VI.     THE   SKIN. 

646.  The  whole  body  of  the  animal  is  externally  sui- 
rounded  by  the   solid  elastic  skin,  which  consists  of  a 
thick  tissue  of  cells,  between  which  are  small  openings 
(pores).       The    annexed    figure 
Fig>  219>  represents  a  piece  of  human  skin 

about  the  size  of  a  mustard-seed, 
as  it  appears  under  a  powerful 
magnifying-glass.  Partly  an  oily 
substance,  and  partly  a  watery 
perspiration,  together  with  some 
carbonic  acid,  are  separated  from 
the  body  through  the  pores. 

Experiment.  —  Put  a  piece  of  fresh  animal  skin  in 
water ;  it  swells  up  in  it  without  dissolving ;  if  kept  for 
some  time,  it  passes  over  into  an  offensive  putrefaction. 
If,  however,  the  skin  is  boiled  for  some  hours  with  wa- 
ter, the  largest  part  of  it  dissolves,  and  we  obtain  a 
liquid  which,  on  cooling,  coagulates  into  a  tremulous 
jelly.  When  dried,  this  forms  the  well-known  glue. 
The  skin  does  not  contain  glue  ready  formed,  but 
a  tissue,  which  first,  after  long  boiling,  passes  over 
into  glue,  and  has  received  the  name  of  gelatinous 
tissue. 


644 


ANIMAL    MATTER. 


647.   Gelatine  forms  a  principal  constituent  of  the 
animal  body,  for  it  is  found  in  almost  all  parts  of  r1 
which  do  not   belong  to  the  albuminous  substances 
for  instance,  in  the  interior  skin,  the  muscles,  the  ten- 
dons  and  ligaments,  the  bones,   horns,  &c..    Its  com 
position    is   very   nearly   that  of  albumen    or   animal 
fi brine ;  like  these,  it  is  very  rich  in  nitrogen,  and  con- 
tains also  some   sulphur,  btat  it  is  distinguished  from 
them  essentially  by  its  properties,  and  its  behaviour  to- 
wards other  substances. 

Glue.  —  The  common,  amorphous  glue  is  mostly 
prepared  from  refuse  skins  or  bones,  either  by  extrac- 
tion with  hot  water,  or,  better,  by  the  pressure  of  steam 
(digesting).  The  concentrated  hot  solution  is  then  al- 
lowed to  settle,  and  the  thin  liquor  yields,  on  cooling,  a 
stiff  jelly,  which  is  cut  by  wires  into  thin  cakes,  and 
placed  to  dry  upon  packthread  nettings,  which  give  it 
the  well-known  grooved  appearance. 

Experiment.  —  If  you  allow  glue  to  lay  in  cold  water, 
it  swells  up  into  an  opaque  soft  mass ;  if  you  then 
heat  it,  you  obtain  a  complete  transparent  solution, 
which,  even  when  a  hundred  times  diluted,  stiffens  on 
cooling.  The  application  of  glue  as  an  adhesive  me- 
dium is  well  known;  its  adhesive  power  is  much  in- 
creased by  adding  to  it  white  lead  (Russian  glue)  or 
borax  (about  an  ounce  or  an  ounce  and  a  half  to  a 
pound  of  glue). 

Isinglass,  also,  is  one  of  the  gelatinous  substances. 
This  consists  of  the  inner  skin  of  several  fishes,  par- 
ticularly of  the  sturgeon,  which,  after  being  cleansed,  is 
dried  and  brought  into  the  market  in  the  form  of  plates, 
or  of  sticks  twisted  into  the  shape  of  a  horseshoe. 
On  boiling,  a  colorless  or  odorless  gelatinous  solution 
is  obtained  from  it,  which  is  much  used  as  an  adhesive 


THE    SKIN.  645 

medium,  or  when  smeared  upon  taffety  as  court-plaster, 
or  mixed  with  the  juices  of  fruits  and  sugar  for  the 
preparation  of  jellies. 

The  antlers  of  the  deer  are  likewise  rich  in  gelatine, 
and  on  this  account,  when  rasped,  yield,  by  long  con- 
tinued boiling  with  water,  a  liquid  which  stiffens  in 
the  cold  (hartshorn  jelly). 

Small  quantities  of  gluten  occur  also  in  broth,  and 
in  roast-broth,  and  impart  to  them,  especially  to  the 
latter,  the  property  of  stiffening  in  the  cold  to  a  tremu- 
lous jelly. 

648.  Gelatine  and  Tannic  Acid.  —  Experiment.  —  If 
you  pour  some  tincture  of  galls  upon  a  solution  of 
gelatine,  or  upon  a  decoction  of  meat,  you  obtain  a 
flaky  precipitate,  a  combination  of  gelatine  with  tan- 
nic  acid,  which  is  insoluble  in  water,  and  may  remain 
exposed  to  the  moist  air  without  passing  into  putrefac- 
tion. For  this  reason,  gelatine  is  an  excellent  means 
for  clarifying  liquids,  for  instance,  wine,  &c.,  from  any 
tannin  that  they  may  contain. 

But  this  action  of  tannic  acid  upon  gelatine  is  of 
far  more  importance,  as  it  may  be  used  for  converting 
animal  skins  into  leather.  The  gelatine  of  the  skin  is 
thus  altered,  as  the  gelatine  in  the  experiment  was, 
when  the  skins  are  packed  in  layers  with  ground  oak 
or  pine  bark  (tan)  in  vats,  and  allowed  to  remain 
moistened  with  water  till  they  are  quite  saturated  with 
the  brown  tannin  of  the  bark  (tanning'}.  This  penetra- 
tion takes  place  more  rapidly  by  forcibly  pressing  the 
liquid  containing  tannin  into  the  skin  (quick-tanning'). 
The  brown  sole  and  upper  leather  consist,  accordingly, 
of  cellular  tissue,  the  gelatine  of  which  has  become  in- 
timately combined  with  the  tannic  acid;  it  is  irj\v, 
especially  when  it  is  saturated  with  oil  or  fat,  pliable 


646 


ANIMAL    MATTER. 


supple,  and  almost  impervious  to  water;  nor  when 
moist  does  it  undergo  putrefaction. 

Skins  are  converted  in  another  manner  into  leather, 
by  means  of  certain  salts,  most  frequently  by  laying 
them  in  a  solution  of  alum  and  common  salt,  and 
afterwards  working  them  with  fish-oil  and  other  fats ; 
the  leather  prepared  in  this  way  is  white,  and  is  softer 
and  more  supple  than  the  former  (tawing).  The  still 
softer  wash  or  chamois  leather  is  obtained  by  working 
the  skins  a  long  time  with  fat.  In  this  way  the  Indians 
also  convert  the  skins  of  animals  into  soft  leather,  by 
kneading  them  with  the  brains  of  animals  that  have 
been  steeped  in  hot  water,  until  the  fat  contained  in 
the  brains  has  been  absorbed  by  the  skin. 

If  the  softened  and  scraped  skins  are  stretched  in 
frames,  and  rubbed,  while  drying,  with  pumice-stone, 
till  they  are  quite  smooth,  the  thin,  translucent,  stiff, 
and  elastic  parchment  is  obtained  (hog-skin).  By  rub- 
bing with  chalk,  the  parchment  becomes  white  and 
opaque,  by  smearing  with  white  lead  and  varnish,  pol- 
ished and  smooth  (writing-parchment). 

649.  Before  the   animal  skins  can   be  subjected  to 
either  of  the  operations  just  described,  they   must  be 
freed  from  the  hair.     This  is  easily  done  by  scraping, 
after  the  skin  has  been  decomposed  either  by  the  influ- 
ence of  moisture  and  heat,  or  by  caustic  potassa.     Sul- 
pliuret  of  calcium  may  also  be  used  for  this  purpose 
(§  405). 

650.  Gelatine,  like  other  animal  substances  in  the 
presence  of  air  and  water,  very  readily  passes  into  de- 
cay or  putrefaction,  and  yields  thereby,  since  it  is  very 
rich  in  nitrogen,  much  ammonia  ;  therefore  it  will   not 
appear^range  that  it  powerfully  promotes  the  growth 
of  plants.     Its  effect  may  be  observed  in  a  truly  sur- 


THE    SKIN. 

prising  manner  in  the  hyacinth,  if  it  is  occasionally 
watered  with  a  thin  solution  of  glue,  or  if  the  bulbs 
are  surrounded  with  horn-shavings  when  planted  in  the 
earth. 

651.  If  gefetine  is  boiled  for  some  time  with  potassa 
lye,  there  is  formed  from  it,  together  with  some  other 
products  of  decomposition,  a  peculiar  substance,  crys- 
tallizing in  needles  ;  it  has  a  very  sweet  taste,  and  has 
received  the  name  of  sugar  of  gelatine,  or  glycocoll. 

652.  There  is  a  kind  of  gelatine  which  varies  some- 
what in  its  properties  from  common  gelatine;   it  is  ob- 
tained from   young,   not  yet  fully  hardened  bones,  and 
from  the  cartilaginous  parts  of  the  animal  body,  —  for 
instance,  from  the  cartilages  of  the  windpipe,  of  the 
nose,  &c.,  —  by  long  boiling  with  water.     This  kind  of 
gelatine  has  received  the  special  name  of  chondrine. 

653.  Horny  Matter.  —  The  hair,  wool,  bristles,  feath- 
ers, nails,  claws,  hoofs,  horns,  scales,  &c.,  which  often 
cover  the  skin  of  animals,  are  not  dissolved  by  boiling 
with  water  into  gelatine;  they  very  much  resemble  the 
latter  in  their  constitution,  but,  besides  nitrogen,  they 
contain  also  some  sulphur.    Their  containing  sulphur  is 
the  reason  why  they  become  black,  when  heated  with 
a  solution  of  lead,  since  a   dark  sulphuret  of  lead  is 
formed.      Wool  consists  of  hollow  yellowish  tubes,  cov- 
ered with  fat.     By  washing  with  putrid  urine,  or  soap- 
water,  the  fat  may  be  removed ;  but  by  sulphurous  acid 
the  yellow  color  is  converted  into  white  (chlorine  is  not 
applicable  to  the  bleaching  of  wool).     The  fibres  of 
wool,  as  well  as  those  of  silk,  likewise  having  an  ani- 
mal origin,  have  a  far  greater  affinity  for  coloring  mat- 
ter than  the  vegetable  fibres  linen  or  cotton  have  ;  and 
this  is  the  reason  why  woollen  and  silk  stuffs  may  be 
more  easily  or  permanently  dyed  than  cotton  or  linen. 


648  ANIMAL    MATTER. 

By  boiling  with  lye,  all  the  above-named  animal  sub- 
stances, consisting  of  horny  matter,  may  be  entirely 
dissolved. 


VH.    THE  BONES. 

The  bones  forming  the  solid  skeleton  of  the  animal 
body  consist,  one  third  of  organic  gelatinous  matter, 
and  two  thirds  of  inorganic  matter  (bone-earth). 

654.  Bone-earth.  —  Experiment.  —  Put   a    piece    of 
beef-bone,  which  has  been  weighed,  into  a  furia ace-fire, 
and  take  it  out  again  when  it  has  entirely  recovered  its 
white  color ;  the  gelatine  burns  up,  but  the  bone-earth 
remains  behind.     The  bone  burnt  to  whiteness,  which 
has  become  one   third   lighter,  consists  principally  of 
phosphate  of  lime  mixed  with  some  carbonate  of  lime 
(magnesia,  fluoride  of  calcium,  and  chloride  of  sodium). 
This  proportion  between  gelatine   and  bone-earth   is, 
however,  not  unchangeable;  it  varies  in  different  ani- 
mals, and  indeed  even  in  one  and  the  same  animal,  ac- 
cording to  its  age. 

655.  Bone-black.  —  Experiment.  —  If  you  heat  a  bone 
for  some  hours  in  a  crucible  which  is  well  covered  with 
a  piece  of  slate,  it  assumes  a  black  color ;  it  becomes 
bone-black  (ivory-black,  &c.).     As  the  air  in  such  cases 
does  not  have  access  to  the  bones,  only  an  imperfect 
combustion  takes  place,  a  charring   of  the   gelatine ; 
the  bone-earth,  intimately  mixed  with  the  carbon,  re- 
mains behind. 

Experiment.  —  If  you  add  some  diluted  muriatic  acid 
to  the  bone-black,  and  let  it  remain  some  time  in  a 
warm  place,  the  bone-earth  will  be  dissolved,  and  the 
carbon  may  be  separated  by  filtration,  washed,  and 
dried.  From  one  ounce  of  bone-black  only  half  or 


THE    BONES. 


649 


three  fourths  of  a  dram  of  carbon  is  obtained ;  but  this, 
on  account  of  its  minute  state  of  division,  possesses 
such  a  striking  bleaching  power,  that  one  ounce  of 
bone-black  acts  far  more  powerfully  than  the  same 
quantity  of  wood-coal.  If  ammonia  is  added  to  the 
filtered  liquid,  the  dissolved  phosphate  of  lime  is  again 
precipitated  from  it  as  a  white  powder,  because  the 
muriatic  acid  is  neutralized  by  the  ammonia,  and  thereby 
loses  the  capacity  of  holding  the  bone-earth  in  solution. 

656.  Experiment.  —  Put  a  bone  in  a  glass  vessel,  and 
pour  over  it  some  diluted  muriatic  acid ;  the  bone  will 
gradually  become  soft  and  transparent,  and  finally  pass 
into  a  cartilaginous  translucent  mass.      The  way  in 
which  the  muriatic  acid  acts  is  obvious  from  the  former 
experiment ;  it  dissolves  the  bone-earth,  and  the  gelatine 
remains  behind,  since  it  is  insoluble  in  muriatic  acid 
and  in  water.     If  the  gelatine  is  taken  from  the  acid, 
and,  after  having  been  washed,  is  boiled  for  some  time 
with  water,  it  passes  over  into  glue,  and  a  solution  is 
obtained  which  coagulates  on  cooling.     This  method 
is  employed  in  many  factories  for  preparing  glue  from 
bones.     The  acid  solution  of  bone-earth  makes  an  ex- 
cellent manure.     That  bone-earth  is  in  fact  dissolved  in 
the  acid  is  readily  ascertained  by  the  addition  of  am- 
monia. 

657.  In  boiling  out  the  bones  with  water,  not  only  the 
fat  present  in  all  bones,  but  also  the  gelatine  lying  in 
the  external  part,  is  extracted,  and  the  latter  may  be 
entirely   extracted   when   the  boiling  is  performed  in 
tight   vessels,    as.  in  this  case  the  water  is  forced  by 
the  increased  pressure  into   the  interior  of  the  bones. 
Steam,  also,  at  a  great  tension,  operates  in  the  same 
way.     Glue  is  prepared  on  a  large  scale,  according  to 
both  of  these  methods. 

55 


650  ANIMAL    MATTER. 

658.  Bone-dust.  —  Unburnt  bones  ground  to  a  coarse 
powder    (bone-dust),   and    also    white    or   black   burnt 
bones,  have  for  many  years  been  regarded  in  England 
as  an  excellent  manure;  in  Germany  it  is  only  in  more 
recent  times  that  their  economical  value  has  been  rec- 
ognized.    It   is  very  obvious   how   they  enhance   the 
fertility  of  land ;  the  burnt  bones  furnish  the  soil,  by 
means    of    the  bone-earth,   with   two   inorganic   sub- 
stances, lime,  and  phosphoric  acid,  which  every  plant 
requires  for  its  development ;  the  unburnt  bones,  more- 
over, by  means  of  their  gelatinous  matter,  furnish  am- 
monia. 

f 

.  Vm.    THE  SOLID  EXCREMENTS  AND  URINE. 

659.  Those  ingredients  of  the  food  consumed,  which 
are  not  applicable  to  nourishment,  that  is,  which  can- 
not be  converted  into  the  constituents  of  the  animal 
body,  and  those  parts  which  are  separated  from  the 
body  (as  no  longer  serviceable  to  the  vital  process)  by 
the  incessant  process  of  renovation,  which  we  call  life, 
are  either  removed  from  the  body  in  an  aeriform  state, 
by  breathing'  or  insensible  perspiration,  or  in  a  liquid 
form,  as  urine,  or,  finally,  in  a  solid  form,  that  of  the 
solid  excrements.     Both  of  the  last-named  substances 
are  of  great  consequence  in   medicine  and   domestic 
economy ;  in  medicine,  because  the  physician,  in  cases 
of  sickness,  is  frequently   able,  by  their  condition,  to 
ascertain  the  nature  of  a  disease ;  in  domestic  economy, 
because  the  farmer  makes  use  of  them  for  promoting 
the  growth  of  plants. 

The  solid  excrements  (faeces)  consist,  for  the  most 
part,  of  those  constituents  of  the  food  which  are  not 
dissolved  in  the  stomach,  —  not  digested;  in  the  her- 


THE    SOLID    EXCREMENTS    AND    URINE.  601 

bivorous  animals,  principally  of  vegetable  tissue,  chlo- 
rophyll, wax,  and  insoluble  salts  ;  in  the  carnivorous 
animals,  dogs,  for  instance,  frequently  almost  wholly  of 
inorganic  substances,  as  phosphate  of  lime,  magnesia, 
&X3.,  mixed  with  but  a  very  small  quantity  of  organic 
matter.  The  beneficial  influence  of  solid  excrements 
on  vegetation  is  principally  owing  to  the  inorganic 
compounds  contained  in  them  (lime  and  magnesia, 
phosphoric  acid,  and  silicic  acid). 

660.  By  the  urine,  which  is   separated  in  the  kid- 
neys from  the  arterial  blood,  the  soluble  salts  contained 
in  food,  and  also  the  nitrogen,  no  longer  necessary  for 
the  vital  process,  are  removed  again  from  the  body ;  it 
is  natural,  therefore,  that  the  constituents  of  it,  as  like- 
wise of  the  faeces,  should  correspond  exactly  with  the 
food  consumed.     If  this   is    rich  in  soluble  salts,  the 
urine  will  also  be  rich  in  them ;  if  this  contains  only  a 
few  soluble,  but  many  insoluble  salts,  the  urine  will  be 
poor  in  soluble  salts,  while  the  faeces  will  be  rich  in  in- 
soluble salts.     Consequently,  the  amount  of  inorganic 
substances  in  the  animal  excrement  or  manure  may  be 
just  as  accurately  ascertained  from  the  food  which  the 
animal  consumes,  as  from  the  manure  itself.     The  food 
has  only   to   be  burnt,  and  the  remaining  ashes  ex- 
amined ;  those  parts  of  it  which  are  soluble  in  water 
correspond  with  the  salts  in  the  urine ;  those  which  are 
insoluble,  to  the  organic  substances  of  the  fasces.     We 
find  in  the  urine  of  cows  and  horses  principally  alka- 
line carbonates,  muriates,  and  sulphates  (potassa,  soda, 
and  ammonia) ;  in  the  urine  of  men,  moreover,  some 
alkaline  phosphates. 

661.  Nitrogen  is  contained  in  the  urine,  either  in  the 
form  of  urea,  uric  acid,  or  hippuric  acid.      Urine,  like 
the  juice   of  flesh,   contains,   moreover,   creating   and 
creatmine  (§640). 


652 


ANIMAL    MATTER. 


Urea  occurs  in  the  greatest  abundance  in  the  urine 
of  the  higher  animals,  especially  in  the  carnivorous 
quadrupeds.  It  crystallizes  in  colorless  needles,  or 
prisms,  and  is  easily  soluble  in  water.  This  substance 
has  excited  great  scientific  interest,  as  it  is  the  first  or- 
ganic compound  which  has  been  artificially  prepared. 
Thus,  it  was  found  that  cyanate  of  ammonia,  without 
losing  any  of  its  constituents,  or  receiving  any  new 
ones,  was  converted  merely  by  heat  into  urea. 

From  Cyanic  Acid  =  Carbon,  Oxygen,  Nitrogen, 

and     Ammonia      =  Nitrogen,  Hydrogen, 

was  formed  Urea. 

In  a  practical  point  of  view,  that  decomposition 
which  urea  undergoes  in  urine,  when  the  latter  putre- 
fies by  long  standing  in  the  air,  is  of  great  importance. 
During  this  decomposition,  the  urea  combines  with  the 
constituents  of  two  atoms  of  water,  and  becomes  there- 
by carbonate  of  ammonia ;  from 

Urea    =  Carbon,  Oxygen,  Nitrogen,  Hydrogen, 
and  Water  =  Oxygen,  Hydrogen, 

are  formed       Carbonic  Acid     and      Ammonia. 

662.  Uric  acid  (liiliic  acid)  predominates  in  the  urine 
of  the  lower  animals;  the  white  excrements  of  birds 
and  snakes  (a  mixture  of  faeces  and  urine)  consist 
chiefly  of  urate  of  ammonia.  In  the  pure  state,  it 
consists  of  fine  white  crystalline  scales,  which  are  dis- 
solved in  water  only  with  extreme  difficulty.  On  ac- 
count of  this  difficult  solubility,  they  sometimes  sepa- 
rate spontaneously  from  the  urine  (gravel  and  urinary 
calculi).  If  the  excrements,  which  are  rich  in  uric  acid, 
are  allowed  to  remain  for  some  time  exposed  to  the  air 
they  will  absorb  oxygen,  and  afterwards  contain  oxalate 
of  ammonia;  if  the  latter  takes  up  more  oxygen,  it 


THE    SOLID    EXCREMENTS    AND    URINE.  653 

passes  over  into  carbonate  of  ammonia.  Thus  is  ex- 
plained why  we  frequently  find  in  some  sorts  of  guano 
only  traces  of  uric  acid,  but  instead  of  it  large  quan- 
tities of  oxalates. 

663.  Guano  (bird-manure). —  Guano,  which  in  recent 
times  has  Keen  in  such  demand  as  a  manure,  owes  its 
efficacy  chiefly  to  the  uric  acid  contained  in  it,  or,  in 
so  far  as  this  has  already  undergone  decomposition,  to 
the  ammoniacal  salts  formed  from  it,  and  in  part  also  to 
inorganic  salts  (sulphate,  phosphate,    and    muriate  of 
potassa,  soda,  lime,  magnesia,  &c.)  present  in  it.     On 
account  of  the  great  difference  in  the  article,  it  is  indis- 
pensable that  the  farmer  should  test  it  before  its  appli- 
cation.    This  is  done  with  sufficient  accuracy  for  agri- 
cultural purposes  in  the  following  way. 

Experiment  a.  —  Pour  some  strong  vinegar  over 
guano ;  no  perceptible  effervescence  should  ensue.  A 
brisk  effervescence  .would  indicate  an  admixture  of  car- 
bonate of  lime. 

Experiment  b.  —  Heat  half  an  ounce  of  guano  in  an 
iron  spoon  over  an  alcohol  lamp,  or  upon  glowing  char- 
coal, till  it  is  burnt  to  a  white  ashes;  good  guano 
should  only  leave  behind,  at  the  most,  one  dram  of 
ashes.  How  much  alkaline  salt  this  ashes  contains 
may  be  ascertained  by  extraction  with  hot  water ;  what 
remains  are  earthy  (lime  and  magnesia)  salts.  The  in- 
ferior sorts  of  guano  often  yield  after  burning  three 
quarters  of  ashes. 

Experiment  c.  —  Treat  half  an  ounce  of  pulverized 
guano  several  times  with  hot  water,  and  decant  the 
liquid  after  it  has  become  clear  on  settling ;  then  dry  arid 
weigh  the  muddy  mass  which  finally  remains ;  it  should 
not  weigh  more  than  a  quarter  of  an  ounce. 

664.  Hippuric  Acid. —  This  azotized  acid  always  o*> 

55* 


654  ANIMAL    MATTER. 

curs  in  the  urine  of  herbivorous  animals ;  it  crystallize* 
in  long  white  needles,  and  is  difficultly  soluble  in  water. 
On  the  putrefaction  of  the  urine,  it  is  converted  into 
benzoic  acid  and  ammonia. 

Human  urine  contains  the  above-named  compounds 
rich  in  nitrogen,  —  urea,  uric  acid,  and  hippuric  acid  ; 
the  first,  urea,  in  the  largest  quantity. 

665.  When  urine  remains  for  some  time  exposed  to 
the  air,  it  undergoes  a  decomposition,  by  which  volatile 
substances  having  a  disagreeable  odor  are  formed ;  it 
passes  into  putrefaction.  It  is  obvious  from  what  has 
been  stated,  that  carbonate  of  ammonia  is  to  be  regarded 
as  the  principal  product  of  this  decomposition  (putrid 
urine  contains,  moreover,  creatine).  Putrid  urine  may, 
therefore,  be  employed  for  the  cleansing  of  wool,  and 
for  the  preparation  of  chloride  of  ammonium  (§  233). 
This  change  takes  place  when  the  urine  is  collected  in 
manure-heaps,  or  is  poured  upon  the  soil.  To  prevent 
the  evaporation  of  the  volatile  carbonate  of  ammonia, 
it  is  well  to  add  gypsum,  diluted  sulphuric  acid,  or 
green  vitriol,  from  time  to  time,  to  the  manure-heaps,  by 
which  means  sulphate  of  ammonia  is  formed,  which 
does  not  escape  at  the  ordinary  temperature.  In  this 
respect,  also,  an  addition  of  substances  rich  in  carbon, 
for  instance,  bone-black,  earthy-brown  coal,  peat,  &c., 
acts  very  beneficially,  because  the  coal  first  retards  the 
putrid  decomposition,  and  afterwards  retains  the  gases 
hereby  formed  (carbonic  acid,  ammonia,  sulphuretted 
hydrogen,  &c.).  The  inorganic  salts  of  the  urine,  and 
of  the  solid  excrements,  are  not  essentially  changed  by 
the  putrefaction.  To  these  salts  and  to  the  nitrogen 
are  principally  to  be  ascribed  the  beneficial  effects  which 
animal  manure  exercises  on  the  fertility  of  our  fields. 


RETROSPECT.  655 

RETROSPECT  OF  ANIMAL  MATTER  IN  GENERAL. 

1.  A  constant  motion  is  taking  place  in  the  living 
animal,  as  well  as  in  the  living  plant,  —  an  incessant 
receiving  (eating,  drinking,  and  breathing),  changing 
(digestion,  assimilation),  and  separating  (secretion,  ex- 
cretion) of  aeriform,  liquid,  and  solid  bodies. 

2.  In  a  chemical  point  of  view,  animal  life  is  distin- 
guished principally  from  vegetable  life  by  the  uninter- 
rupted reception  of  oxygen,  and  separation  of  carbonic 
acid  and  water.     (Among  the  Infusoria,  however,  there 
are  some  which  exhale  oxygen.)      During   the  life  of 
plants,  on  the  contrary,  carbonic  acid  and  water  are  re- 
ceived, and  oxygen  separated. 

3.  Besides  water,  air,  and  some  salts,  those  substances 
only  serve  for  the  nutrition  of  the  animal  body  which 
are  produced  by  means  of  vegetable   or   animal    life. 
The   plant  consumes  carbonic  acid,  the  animal  vege- 
table tissue,  sugar,  gum,  fat,  &c.  ;  the  plant  consumes 
ammonia,  the  animal   albuminous  substances,  for  in- 
stance, gelatine,  albumen,  caseine,  flesh,  blood,  &c. 

4.  The   first   series   of  the    above-named    means   of 
nourishment,  those  rich  in  carbon,  serves  for  the  main- 
tenance of  the  respiratory  or  destructive  processes,  and 
for  the  generation  of  animal  heat  (elements  of  respi- 
ration) ;  the  second  class,  that  of  the  means  of  nourish- 
ment rich   in    nitrogen,    serves   for  the   maintenance 
of  the  nutritive  or  formative  process   (plastic  elements 
of  nutrition). 

5.  Animal  substances  may  be  divided  :  — 
I.  According  to  their  composition,  — 

a.)   Into  non-azotized  substances  (fat,  sugar  of  milk, 


b.)  Into  azotized,  albuminous  substances  (albumen, 
caseine,  flesh,  fibrine,  &c.). 


656  ANIMAL    MATTER. 

c.)  Into  azotized  gelatinous  substances  (gelatine  of 
the  bones,  ligaments,  gristle,  &c.). 

d.)  Into  azotized  excretory  substances  (urea,  uric  acid, 
Lippuric  acid,  &c.). 

II.  According  to  their  occurrence  and  their  production 
in  the  animal  body,  — 

a.)   Into  products  of  the  process  of  digestion. 

b.)      «  «  «  «  breathing. 

c.)   Constituents  of  the  red  blood. 

d.)  "  of  the  white  blood  (lymph). 

e.)  «  of  the  flesh,  &c. 

/.)  "  of  the  bones,  &c. 

g.)  "  of  the  skin,,  hair,  &c. 

h.)  "  of  the  secretory  and  excretory  prod- 

ucts (gall,  milk,  urine,  &c.). 

6.  The  changes  of  animal  matter  by  the  influence  of 
heat,  water,   air,   acids,  bases,  &c.,  exceed  in   variety 
those  of  vegetable  matter,  since  they  are  far  more  com- 
plex than  the  latter;   they   mainly  agree   with   those 
which  the  azotized  and  sulphurized  vegetable  substan- 
ces experience. 

7.  The   spontaneous  changes  of  animal  and  vege- 
table matter  may  be  arrested,  — 

a.)  By  removal  of  the  water  (drying,  baking,  &c.). 

b.)  By  exclusion  of  air  ( Appert's  method  of  preserva 
tion,  bottling  of  beer,  wine,  &c.). 

c.)  By  reducing  the  temperature  below  the  freezing 
point  (refrigerators,  &c.). 

d.)  By  antiseptics ;  for  instance,  common  salt,  nitre 
(salting),  wood- vinegar,  creosote  (smoking),  alcohol, 
sugar,  charcoal,  and  arsenical,  mercurial,  and  other 
metallic  compounds. 


A   SYNOPSIS 

OP  THE  MOST  IMPORTANT  TESTS  FOR  ASCERTAINING 
THE  PRESENCE  OF  THE  MORE  COMMON  CHEMICAL 
COMPOUNDS,  ESPECIALLY  WHEN  IN  SOLUTION. 


1.  Alkalies  and  their  Salts. 

THESE  are  not  precipitated  by  carbonate  of  ammonia, 
sulphuretted  hydrogen  (H  S),  or  sulphuret  of  ammo- 
nium (N  H3J  H  S). 

2.   Salts  of  Potassa. 

Tartaric  acid,  in  excess  and  in  a  concentrated  solu- 
tion, produces,  especially  after  violent  agitation,  a  white 
crystalline  precipitate.  (Tartar,  §  194.) 

Platinum  solution  gives  a  yellow  crystalline  precipi- 
tate. ( Chloride  of  platinum  and  potassium,  §  394.) 

3.  Salts  of  Soda. 

Antimoniate  of  potass  a  produces,  in  neutral  or  alka- 
line solutions  of  soda  salts,  a  white  precipitate.  (Anti- 
moniate  of  soda,  §  404.) 

4.  Salts  of  Ammonia. 
Caustic  lime  or  caustic  potassa,  especially  on  heating 


658  CHEMICAL    TESTS. 

liberates  the  ammonia,  which  is  easily  recognized  by 
its  pungent  odor.  Heated  on  platinum  foil,  the  salts  of 
ammonia  are  readily  volatilized.  (§  229.) 

Platinum  solution  reacts  in  the  same  manner  as  with 
potassa  salts.  (§  392.) 

5.  Alkaline  Earths. 

These  are  precipitated  by  carbonate  of  ammonia,  as 
carbonates  of  a  white  color,  but  not  by  H  S  or  N  H3, 
HS. 

6.  Salts  of  Baryta  and  Strontia. 

Sulphuric  acid  produces  a  white  precipitate,  insoluble 
in  acids  (sulphate  of  baryta  and  of  strontia).  The  ba- 
ryta salts  impart  a  yellowish  color,  and  the  strontia  salts 
a  crimson  color,  to  the  flame  of  alcohol.  (§  248.) 

7.  Salts  of  Lime. 

Sulphuric  acid  produces  only  in  concentrated  solu- 
tions of  lime  a  precipitate,  which  is  redissolved  in  a 
large  proportion  of  water.  (§  241.) 

Oxalic  acid  and  ammonia  indicate  mere  traces  of  lime 
by  a  milky  turbidness.  (Oxalate  of  lime,  §  197.) 

8.  Salts  of  Magnesia. 

Sulphuric  acid  causes  no  precipitate  or  turbidness. 
(§  249.) 

Phosphate  of  soda  and  ammonia  produce,  but  not  im- 
mediately, in  diluted  solutions,  a  white  crystalline  pre- 
cipitate. (Phosphate  of  magnesia  and  ammonia,  §  251.) 

9.  Sails  of  Alumina. 

These  are  precipitated  by  ammonia,  carbonate  of  am* 
monia,  and  also  by  N  H3,  H  S,  as  hydrate  of  the  oxida 


CHEMICAL    TESTS.  659 

of  alumina.  Potassa  in  excess  dissolves  the  hydrate  of 
oxide  of  alumina,  which  is  again  precipitated  by  chloride 
of  ammonium.  (§  260.)  They  are  colored  blue  on  being 
heated  to  redness  with  cobalt  solution.  (§  262.) 

10.  Metallic  Salts. 

Ammonia  precipitates  from  their  solutions  the  oxides 
as  hydrates ;  carbonate  of  ammonia  also  precipitates 
them  (partly  as  carbonates,  and  partly  as  hydrated  ox- 
ides). 

H  S^  added  to  an  acid  solution  precipitates  the  fol- 
lowing metallic  oxides  as  sulphurets:  — 

a.)  Black  ;  lead,  bismuth,  copper,  silver,  mercury, 
platinum,  gold. 

b.}   Dark  brown  ;  tin  (protoxide). 

c.)   Orange  ;  antimony. 

d.)   Yellow  ;  tin  (peroxide),  cadmium,  arsenic. 

Of  these,  the  sulphurets  of  platinum,  gold,  tin,  anti- 
mony, and  arsenic,  are  soluble  in  N  H3,  H  S. 

N  H3,  H  S  precipitates  also  as  sulphurets  the  follow- 
ing, which  are  not  precipitated  by  sulphuretted  hydro- 
gen alone  from  their  acid  solutions:  — 

a.)   Black ;  iron,  cobalt,  nickel. 

b.)  Flesh-colored  ;  manganese. 

c.)  White  ;  zinc  (also  alumina  and  oxide  of  chro- 
mium as  hydrates). 

11.  Salts  of  Protoxide  of  Iron. 

Ammonia;  a  greenish-white  precipitate,  passing  to 
dark  green,  and  finally  to  reddish-brown.  (Hydrated 
protoxide  of  iron,  §  285.) 

Ferrocyanide  of  potassium ;  a  light  blue  precipitate, 
becoming  finally  dark  blue.  (§  292.) 

Tincture   of  nutgalls ;   a  violet  precipitate,   passing 


660  CHEMICAL    TESTS. 

gradually  to  blue-black.    (Tannate  of  protoxide  of  iron 
§  285.) 

12.  Salts  of  Sesquioxide  of  Iron. 

Ammonia;  a  reddish-brown  precipitate.  (Hydrated 
sesquioxide  of  iron,  §  285,) 

Ferrocyanide  of  potassium;  a  dark-.blue  precipitate. 
(Prussian  blue,  §  292.) 

Tincture  of  nutgalls  ;  a  blue-black  precipitate.  (Tan- 
nate of  sesquioxide  of  iron,  §  285.) 

13.  Salts  of  Manganese. 

Ammonia;  a  white  precipitate,  soon  passing  to  light 
arid  then  dark  brown.  (Hydrated  protoxide  of  manga- 
nese, §  300.) 

H  S  ;  a  flesh-colored  precipitate.  (Sulphuret  of  man- 
ganese, §  300.) 

14.  Salts  of  Cobalt. 

Potassa ;  a  blue  precipitate,  gradually  becoming 
green.  (§  307.) 

Blowpipe  ;  melted  with  borax,  they  give  a  blue  bead. 
(Cobalt  glass,  §  304.) 

15.  Salts  of  Nickel. 

Potassa;  a  light  green  precipitate.  (Hydrated  pro- 
toxide of  nickel.  §  307.) 

16.  Salts  of  Zinc. 

Ammonia;  a  gelatinous  white  precipitate  (hydrated 
oxide  of  zinc),  which  redissolves  in  an  excess  of  ammo- 
nia ;  white  sulplmret  of  zinc  is  precipitated  from  this 
solution  by  N  H3,  H  S. 

Blowpipe  ;  heated  with  carbonate  of  soda  upon  char* 


CHEMICAL    TESTS.  661 

coal,  a  yellow  incrustation  is  formed,  which  becomes 
white  on  cooling.     (Oxide  of  zinc,  §  310.) 

17.  Salts  of  Tin. 

Solution  of  gold  causes  in  solutions  of  protoxide  of 
tin  a  purple-red  color  or  precipitate.  (Gold  purple. 
§  322.) 

H  S  ;  in  the  protoxide  solutions,  a  dark-brown  pre- 
cipitate (protosulphuret  of  tin)  ;  in  the  perchloride  so- 
lutions, a  yellow  precipitate.  (Bisulphuret  of  tin,  §  325.) 

18.  Salts  of  Lead. 

Sulphuric  acid ;  a  white  precipitate  insoluble  in  acids. 
(Sulphate  of  lead.)  The  same  is  rendered  black  imme- 
diately by  N  H3,  H  S.  (§  335.) 

Blow-pipe  ;  heated  with  carbonate  of  soda  upon  char- 
coal, malleable  metallic  beads  are  formed,  together  with 
a  yellow  incrustation  upon  the  coal.  (§  331.) 

19.  Salts  of  Bismuth. 

Water,  added  largely  to  solutions  of  bismuth,  causes 
a  white  turbidness,  with  a  precipitation  of  a  basic  salt 
of  bismuth.  (§  347.) 

Blowpipe ;  if  heated  with  carbonate  of  soda  upon 
charcoal,  we  obtain  brittle  metallic  beads.  (§  345.) 

20.  Salts  of  Copper. 

Ammonia  causes  a  greenish-blue  precipitate,  which 
redissolves  in  an  excess  of  ammonia,  forming  a  deep 
blue  liquid.  (§  353.) 

Ferrocyanide  of  potassium  ;  a  purple-red  precipitate. 
(Ferrocyanide  of  copper,  §  292.) 

Polished  iron ;  a  deposition  of  metallic  copper. 
(§  152.) 

56 


662  CHEMICAL    TESTS. 

Blowpipe  ;  when  heated  with  carbonate  of  soda  upon 
charcoal,  and  washed  with  water,  spangles  of  metallic, 
copper  are  obtained.  (§  355.) 

21.  Salts  of  Mercury. 

Potassa  precipitates  from  protoxide  salts  black  pro- 
toxide of  mercury  (§  368)  ;  from  the  peroxide  salts,  yel- 
lowish-red peroxide  of  mercury.  (§  371.) 

Protochloride  of  tin  precipitates  on  boiling  metallic 
mercury.  (§  375.) 

Copper^  on  being  rubbed  with  a  solution  of  mercury, 
assumes  a  silvery  appearance.  (§  369.) 

22.  Salts  of  Silver. 

Muriatic  acid;  a  white,  curdy  precipitate,  soluble  in 
ammonia.  (Chloride  of  silver,  §  381.) 

Blowpipe  ;  heated  with  carbonate  of  soda  upon  char- 
coal, glistening  malleable  metallic  beads  are  formed. 
(§  381.) 

23.  Salts  of  Gold. 

Protochloride  of  tin  /  a  purple-red  precipitate.  (Gold 
purple,  §  388.) 

Green  vitriol ;  a  precipitate  of  gold  powder.    (§  387.) 

\  24.  Salts  of  Platinum. 

Potassa;  a  yellow  crystalline  precipitate.  (Chloride 
of  platinum  and  potassium,  §  394.) 

Blowpipe  ;  reduces  the  salt  to  a  metal.     (§  393.) 

25.  Salts  of  Sesquioxide  of  Chromium. 

Potassa;  a  bluish-green  precipitate  (hydrated  oxide 
of  chromium),  soluble  in  an  excess  of  potassa,  forming 
a  dark  green  solution.  (§  400.) 


CHEMICAL    TESTS.  663 

26.   Salts  of  Chromic  Adid. 

Sugar  of  lead;  a  yellow  precipitate.  (Chrome  yel- 
low, §  399.) 

Sulphurig  acid  and  alcohol;  conversion  of  the  yellow 
or  red  color  into  green  by  heating.  (§  400.) 

27.  Compounds  of  Antimony. 

H  S ;  an  orange-colored  precipitate.  (Sulphuret  of 
antimony,  §  407.) 

Blowpipe;  heated  with  carbonate  of  soda,  brittle 
metallic  globules  are  formed  ;  and  also  white  fumes  and 
a  white  incrustation  upon  the  charcoal.  (§  403.) 

Marsh's  test  (§  418). 

23.   Compounds  of  Arsenic. 

H  S ;  a  yellow  precipitate.  ( Sulphuret  of  arsenic, 
§  416.) 

Reduction  test  (§  413). 
Marsh's  test  (§  417). 

29.  Salts  of  Sulphuric  Acid. 

Chloride  of  barium ;  a  white  pulverulent  precipitate, 
insoluble  in  acids.  (Sulphate  of  baryta,  §  171.) 

Sugar  of  lead;  a  white  precipitate  insoluble  in  di- 
luted acids.  (Sulphate  of  lead,  §  335.) 

30.  Salts  of  Sulphurous  Acid. 

Sulphuric  acid  evolves  a  gas  having  the  odor  of  burn- 
ing sulphur.  (§  174.) 

31.  Salts  of  Phosphoric  Acid. 

Cliloride  of  barium;  a  white  precipitate  soluble  in 
acids. 


664  CHEMICAL    TESTS. 

Silver  solution;  a  yellow  precipitate.  (Phosphate  of 
silver,  §  176.) 

Solution  of  magnesia  and  ammonia ;  a  white  precipi- 
tate. (See  No.  8.) 

32.  Salts  of  Boracic  Acid. 

Chloride  of  barium;  a  white  precipitate  soluble  in 
acids. 

Sulphuric  acid  and  alcohol,  when  heated  with  them, 
present  a  green  flame.  (§  182.) 

33.  Salts  of  Nitric  Acid. 

Indigo  solution  and  sulphuric  acid ;  by  boiling,  the 
feeble  blue-colored  liquid  is  changed  in  color  by  the 
liberated  nitric  acid. 

Glowing  charcoal  causes  a  deflagration  of  the  nitrates. 
(§  207.) 

34.  Salts  of  Chloric  Acid 

Act  like  the  nitrates  towards  solution  of  indigo,  and 
upon  glowing  charcoal ;  but,  when  heated  with  muri- 
atic acid,  they  evolve  the  odor  of  chlorine.  (§  150.) 

35.   Chlorides  or  Salts  of  Muriatic  Acid. 

Silver  solution;  a  white,  curdy  precipitate  of  chloride 
of  silver,  readily  soluble  in  ammonia.  (§  186.) 

Peroxide  of  manganese  and  sulphuric  acid;  evolution 
of  chlorine  on  heating.  (§  151.) 

36.  Iodides. 

Silver  solution;  a  yellowish  precipitate  of  iodide  of 
silver  difficultly  soluble  in  ammonia. 

Peroxide  of  manganese  and  sulphuric  acid  evolve 
iodine  in  violet  fumes.  (§  210.) 


CHEMICAL    TESTS.  605 

Starch  paste  and  nitric  acid;  blue  color.  (Iodide  of 
starch,  §  155.) 

37.  Sulphurets. 

Muriatic  acid  evolves  from  most  of  them  a  gas  hav- 
ing the  odor  of  rotten  eggs.  (H  S,  §§  132,  213.) 

• 

38.  Salts  of  Carbonic  Acid. 

Muriatic  acid  liberates  from  them  with  effervescence 
an  odorless  gas.  (§§  202,  237.) 

Lime-water  is  rendered  milky  by  them.  (Carbonate 
of  lime,  §115.) 

39.  Salts  of  Oxalic  Acid. 

Solution  of  gypsum  causes  a  white  precipitate.  (Ox- 
alate  of  lime,  §  197.) 

Heated  upon  platinum  foil,  they  are  decomposed 
without  charring. ,  (§  197.) 

40.  Salts  of  Tartaric  Acid. 

Potassa  precipitates  tartar,  as  in  No.  2.     (§  194.) 
Heated  on  platinum  foil,  they  are  decomposed  with 

separation  of  much  carbon,  and  give  off  the  odor  of 

burnt  sugar.     (§  194.) 

41.  Salts  of  Acetic  Acid. 

Sulphuric  acid  produces  on  heating  an  odor  of  vin- 
egar. 

Sulphuric  acid  and  alcohol,  an  odor  of  acetic  ether. 
(§  198.) 

Heated,  they  are  charred,  and  give  off  the  odor  of  v'n« 
egar.  (§  198.) 

56* 


TABLE, 


Showing  the  Corresponding  Degrees  of  the  Centigrade  and  Fahrenheit's 
Thermometers. 


Cent.    Fahr. 

Cent.    Fahr. 

Cent.   Fahr. 

Cent.   Fahr. 

o      o 
—50  —58.0 

o      o 
—7    19.4 

o       o 
36     96.8 

0         0 

79   174.2 

—49  —56.2 

—6    21.2 

37     98.6 

80   176.0 

—48  —54.4 

—5    23.0 

38    100.4 

81   177.8 

—47  —52.6 

—4    24.8 

39    102.2 

82   1796 

—46  —50.8 

—3    26.6 

40    104.0 

83   181.4 

—45  —49.0 

—2    28.4 

41    105.8 

84   1  83.2 

—44  —47.2 

—1    302 

42    107.6 

85   185.0 

—43  —45.4 

0    32.0 

43    109.4 

86   1868 

—42  —43.6 

+1    33.8 

44    111.2 

87   188.6 

—41  —41.8 

2    35.6 

45    113.0 

88   190.4 

—40  —40.0 

3    37.4 

46    114.8 

89   1922 

—39  —38.2 

4    39.2 

47    116.6 

90   194.0 

—38  —36.4 

5    41.0 

48    118.4 

91   195.8 

—37  —34.6 

6    42.8 

49    120.2 

92   197.6 

—  36  —32.8 

7    44.6 

50    122.0 

93   199.4 

—35  —30.0 

8    46.4 

51    123.8 

94   201.2 

—34  —29.2 

9    48.2 

52    125.6 

95   2030 

—33  —27.4 

10    50.0 

53    127.4 

96   204.8 

—32  —25.6 

11    51.8 

54    129.2 

97   206.6 

—31  —23.8 

12    5.3.6 

55    131.0 

98   208.4 

—30  —22.0 

13    55.4 

56    132.8 

99   210.2 

—29  —20.2 

14    57.2 

57    134.6 

100   212.0 

—  28  —18.4 

15    59.0 

58    136.4 

101   213.8 

—27  —16.6 

16    60.8 

59    138.2 

102   215.6 

—26  —14.8 

17    62.6 

60    140.0 

103   217.4 

—25  —13.0 

18    64.4 

61    141.8 

104   219.2 

—24  —11.2 

19    66.2 

62    143.6 

105   221.0 

—23  —  9.4 

20    68.0 

63    145.4 

106   222.8 

—22  —  7.6 

21    698 

64    147.2 

107   2246 

—21  —  5.8 

22    71.6 

65    149.0 

108   226.4 

—  20  —  4.0 

23    73.4 

66    150.8 

109   228.2 

—  19  —  2.2 

24    75.2 

67    152.6 

110   2.30.0 

—  18  —  0.4 

25    77.0 

68    154.4 

111   231.8 

—17  -f  1.4 

26    78.8 

69    156.2 

112   233.6 

—16     3.2 

27    80.6 

70    158.0 

113   235.4 

—  15     5.0 

28    82.4 

71    159.8 

114   237.2 

—14     6.8 

29    84.2 

72    161.6 

115   239.0 

-13     8.6 

30    &£.0 

73    1  63.4 

1  1  6   240.8 

—  12    10.4 

31    87.8 

74    165.2 

117   242.6 

—  11    12.2 

32    89.6 

75    167.0 

118   244.4 

—  10    14.0 

33    91.4 

76    168.8 

119   246.2 

—  9    15.8 

34    93.2 

77    170.6 

120   248.0 

—  8    17.6 

35    95.0 

78    172.4 

121   249.8 

667 


Cent.    Fahr. 

Cent.    Fahr. 

Cent.   Fahr. 

Cent.   Fahr. 

o       o 
122    251.6 

0         O 

172    341.6 

o       r 
222   431.8 

272  52L6 

123    253.4 

173    343.4 

223   433  4 

273  523.4 

124    255.2 

174    345.2 

224   435.2 

274  525  2 

125    257.0 

175    347.0 

225   437.0 

275  527.0 

126    258.8 

176    348.8 

226   438  8 

276  528.8 

127    260.6 

177    350.6 

227   440.6 

277  5306 

128    262.4 

178    352.4 

228   4424 

278  532.4 

129    264.2 

179    354.2 

229   4442 

279  534  2 

130    266.0 

180    356.0 

230   4460 

280  536  0 

131    267.8 

181    357.8 

231   447  8 

281  537-8 

132    269.6 

182    359.6 

232   449.6 

282  539.6 

133    271.4 

183    361.4 

233   451  4 

283  541  4 

134    273.2 

184    363.2 

234   453  2 

284  5432 

135    275.0 

185    365.0 

235   455  0 

285  545  0 

136    276.8 

186    366.8 

236   456.8 

286  546.8 

137    278.6 

187    368.6 

237   458  6 

287  548.6 

138    280.4 

188    370.4 

238   460-4 

288  5504 

139    282.2 

189    372.2 

239   462  2 

289  5522 

140    284.0 

190    374.0 

240   4640 

290  554.0 

141    285.8 

191    375.8 

241   465.8 

291  555  8 

142    287.6 

192    377.6 

242   467  6 

292  5576 

143    289.4 

193    379.4 

243   469  4 

293  559.4 

144    291.2 

194    381.2 

244   471.2 

294  561.2 

145    293.0 

195    383.0 

245   473  0 

295  563.0 

146    294.8 

196    384.8 

246   474.8 

296  564  8 

147    296.6 

197    386.6 

247   476.6 

297  5666 

148    298.4 

198    3884 

248   478.4 

298  568  4 

149    300.2 

199    390.2 

249   480  2 

299  570.2 

150    302.0 

200    392.0 

250   482.0 

300  5720 

151    303.8 

201    393.8 

251   483.8 

301   573  8 

152    305.6 

202    395.6 

252   485.6 

302  575  6 

153    307.4 

203    397.4 

253   487.4 

303  577  4 

154    309.2 

204    399.2 

254   489.2 

304  579.2 

155    311.0 

205    401.0 

255   491.0 

305  581.0 

156    312.8 

206    402.8 

256   492.8 

306  5828 

157    314.6 

207    404.6 

257   494  6 

307  584.6 

158    316.4 

208    406.4 

258   496.4 

308  586-4 

159    318.2 

209    408.2 

259   498.2 

309  588.2 

160    320.0 

210    410.0 

260   500.0 

310  5900 

161    321.8 

211    411.8 

261   501.8 

311  591.8 

162    323.6 

212    413.6 

262   503.6 

312  5936 

163    325.4 

213    415.4 

263   505.4 

313  595.4 

164    327.2 

214    417.2 

264   507.2 

314  597.2 

165    329.0 

215    419.0 

265   5090 

315  5990 

166    330.8 

216    420.8 

266   5108 

316  6008 

167    332.6 

217    422.6 

267   512.6 

317  602.6 

168    334.4 

218    424.4 

268   514.4 

318  604-4 

169    336.2 

219    426.2 

269   5162 

319  606.2 

170    338.0 

220    428.0 

270   518.0 

320  608-0 

171    339.8 

221    429.8 

271   519.8 

CHEMICAL  SYMBOLS  AND  EQUIVALENTS, 


Aluminum 

Al  =   13.7 

Nickel 

Ni  =   29.6 

Antimony 

Sb  =129 

Niobium 

Nb 

Arsenic 

As=   75 

Nitrogen 

N    =   14 

Barium 

Ba=   68.5 

Norium 

No 

Bismuth 

Bi  =213 

Osmium 

Os  =    99.6 

Boron 

B    =    10.9 

Oxygen 

O=8 

Bromine 

Br  =  80 

Palladium 

Pd  =   53.3 

Cadmium 

Cd=  56 

Pelopium 

Pe 

Calcium 

Ca  =  20 

Phosphorus 

P     =   32 

Carbon 

C    =     6 

Platinum 

Pt  =    98.7 

Cerium 

Ce  =  47 

Potassium 

K    =   39.2 

Chlorine 

Cl  =  35.5 

Rhodium 

R    =   52.2 

Chromium 

Cr  =   26.7 

Ruthenium 

Ru  =   52.2 

/Cobalt 

Co  =   29.5 

Selenium 

Se  =   39.5 

Copper 

Cu  =  31.7 

Silicium 

Si    =   21.3 

Didvmium 

D 

Silver 

Ag=  108.1 

Erbium 

E 

Sodium 

Na  =   23 

Fluorine 

Fl  =  18.9 

Strontium 

Sr  =   43.8 

Glucinum 

G    =     4.7 

Sulphur 

S     =    16 

Gold 

Au  =  197 

Tantalum 

Ta  =  184 

Hydrogen 

II    =     1 

Tellurium 

Te  =   64.2 

lo  line 

I     =127.1 

Terbium 

Tb 

Iridium 

Ir    =   99 

Thorium 

Th=    59.6 

>,Iron 

Fe  =  28 

Tin 

Sn  =    59 

Lanthanium 

La 

Titanium 

Ti  =   25 

Lead 

Pb  =103.7 

Tungsten 

W  =   95 

Lithium 

Li  =     6.5 

Uranium 

U    =    60 

Magnesium 

Mg=   12.2 

Vanadium 

V     ra     68.6 

Manganese 

Mn=   27.6 

Yttrium 

Y 

Mercury 

IIg  =  100 

'Zinc 

Zn  =  32.6 

Molybdenum 

Mo=   46 

Zirconium 

Zr  =    22.4 

N.  B  —  The  atomic  weights  and  equivalents  arc 

assumed  to  be  equal. 

INDEX. 


INDEX 


[The  numbers  refer  to  the  sections.] 


Absinthine,  589. 
Acetic  acid,  198. 

*»      ether,  507. 
Acetometer,  514. 
Acetyle,  513. 
Acid  oxides,  66. 

"    radicals,  199. 

"    salts,  197. 
Acids,  66,  76,  159,  199,  267 

"     fat,  542. 

"     hydrogen,  184. 

"     organic,  193,  598. 

"     oxygen,  159. 
Aconitine,  597. 
Acroleine,  547. 
Adhesion,  106. 
Affinity,  chemical,  5,  89,  146, 192. 

"       disposing,  89,  146. 

"       of  the  metalloids,  192. 
After-fermentation,  488. 
Aggregation,  19. 
Air,  90. 

"  composition  of,  100,  101. 
"  current  of.  98,  111. 
"  expansion  of,  97. 
Alhumen,  477,  622. 
Alcohol,  482,  498. 

"       burning  of,  121. 
"       flame,  121. 
"       lamp,  112,  121. 
"       \veighing~of,  500. 
Alcoholometer,  500. 
Aldehyde,  512. 
Alizarine,  591. 
Alkalies,  201,  236. 


Alkali-metals,  201. 

Alkalimeter,  202. 

Alkaline  earths,  237,  251. 

Alkaloids,  596. 

Alkanet-root,  591. 

Allotropy,  108. 

Alloys,  305,  317,  346,  364,  378  37» 

383,  409. 

Almonds,  oil  of,  535. 
Aloes,  582. 
Alum,  261. 
Alumina,  260. 

"         silicate  of,  258. 
"         sulphate  of,  259. 
Aluminum,  252. 
Amalgamation,  process  of,  382. 
Amalgams,  378. 
Amber,  571. 
Ammonia,  227,  230. 

"         as  food  of  plants,  614. 
"         by  dry  distillation,  228. 
"         carbonate  of,  232,  665. 
"      .   from  decay,  233, 479,  665 
"         liniment,  541. 
"         salts  of,  as  manure,  235. 
"          water  of,  230. 
Ammonium,  236. 

chloride  of,  229. 
sulphuret  of,  231. 
Amorphism,  127,  129,  475. 
Amygdaline,  589. 
Analysis,  7. 

"        elementary,  435. 
Aniline,  597. 
Animal  fats,  536.        * 
"       fibrine,  636. 
«      life,  619. 


672 


INDEX. 


Animal  matter,  620. 
Animals,  food  of,  639. 
Anthracite,  442. 
Antichlorine,  174. 
Antimoniuretted  hydrogen,  418. 
Antimony,  402. 

"         oxide  of,  403. 
Antimony-glance,  prism atoidal,  407. 
Antlers  of  the  deer,  647. 
Aqua  regia,  188. 
Arable  land,  255,  612. 

"         "     estimation  of,  256. 

"         "      humus  in,  444,  612. 

"         "     inorganic  matter  in,  612. 

"         «     lime  in,  612. 
Archil,  594. 
Areometer,  16. 
Arrack,  496. 
Arrowroot,  455. 
Arsenic,  410. 

"        test  for,  413,  417. 

"        white,  412. 
Arseniuretted  hydrogen,  417. 
Artesian  wells,  252. 
Ashes,  201,  608. 

"      of  plants,  607. 
Asphaltum,  442,  571. 
Assafcetida,  582. 
Assaying,  382. 
Atmosphere,  90. 

"  pressure  of,  91. 

Atomic  weights,  274. 
Atoms,  274. 

"     changes  of,  274,  280,  475. 

"     grouping  of,  274. 
Atropine,  597. 
Aurum  musivum,  325. 


B. 

Baking,  516. 

Balsam,  568. 

Barium,  248. 

Barley,  germination  of,  426. 

Barm,  488. 

Barometer,  93. 

Baryta,  248. 

"        compounds  of,  248. 
Bases,  69,  267. 

"      organic,  596. 
Basic  radicals,  199. 

"    oxides,  69. 
Bast,  430. 
Beans,  germination  of,  426. 


Beer,  487. 
Bees-wax,  539. 
Bell-metal,  364. 
Benzoin,  570. 
Bismuth,  345. 
Bitumen,  571. 
Bleaching,  152,  174,429. 
Blood,  636. 

"      coloring  matter  of,  636. 
Blowpipe,  181. 
Blue  liquid,  353. 
Bogs,  252. 
Boiling,  34. 

"       by  steam,  36. 

"        of  meat,  642. 

"        of  water,  34,  95,  96 
Bone-black,  107. 
Bone-dust,  658. 
Bones,  144,  176,  654. 
Boracic  acid,  180. 
Borax,  225,  351. 
Brandy,  491. 
Brass,  364. 
Braziline,  591. 
Brazil  wood,  591. 
Bread,  517. 
Bremen  blue,  352. 
Bromine,  156. 
Bronze,  364. 
Broth,  643. 

Buckthorn  berries,  592. 
Butter,  631. 
Butyric  acid,  515. 

"      ether,  507. 


C. 

Cadmium,  315. 
Caffeine,  597. 
Calamine,  313. 
Calcium,  237. 

"        and  chlorine,  246. 
Calico-printing,  595. 
Calomel,  370. 
Cain  peachy- wood,  594. 
Camphor,  401,  553. 
Candy,  470. 
Cane-sugar,  470. 
Cannon-metal,  364. 
Caoutchouc,  584. 
Capillary  attraction,  106. 
Caput  mortuum,  276. 
Carat,  383. 
Carbon,  103,  166. 


INDEX. 


673 


Carbonic  acid,  63,  109, 164. 

"  "    as  nutriment  of  plants, 

614. 

"     from  respiration,  167. 
"  "    in  the  air,  101. 

Carbonic  oxide  gas,  110. 
Carbonization,  104,  119,  436. 
Carmine,  blue,  994. 

"        red,  591. 
Carthamine,  591. 
Caseine,  477,  626. 
Cassel  yellow,  336. 
Catalysis,  459. 
Cement,  bydraulic,  239. 
Chalk,  237. 
Charcoal,  104. 
Cheese,  632. 

Chemical  combination,  law  of,  70, 267. 
"       force,  5. 
"       processes,  1. 
"       symbols,  88. 
Cherry  gum,  467. 
Chloric  acid,  178. 
Chloride  of  antimony,  152,  405. 

barium,  248. 
"  calcium,  246. 
"  copper,  152,  359. 

"  gold,  152.  385, 

"  iron,  186,  289. 

lead,  336. 
lime,  244. 
magnesium,  251. 
manganese,  150,  299. 
mercury,  370,  373. 
platinum,  391. 
potassium,  209. 
silver,  381. 
sodium,  153,  215. 
tin,  319. 
zinc,  152. 
Chlor  des,  different,  154. 

metallic,  152,  186. 

"        retrospect  of,  4 18. 
Chlorine,  150. 

"        water,  150. 
Chlorophyll,  593. 
Chondrine,  647. 
Chromate  of  potassa,  398. 
Chrome-yellow,  399. 
Chromic'acid,  401. 
Chromium,  397. 

"          sesquioxide  of,  400. 
Cinchonine;  597. 
Cinnabar,  376. 
Citric  acid,  600. 

57 


Clay,  252. 

"     ware,  257. 
Coal,  104,  107. 
"    brown,  448. 
"     pit,  448. 
Cobalt,  303. 
Cochineal,  591. 
Cocoa-nut  oil,  535. 
Cognac,  486. 
Cohesion,  19. 
Coke,  107,  118,441. 
Colchicine,  597. 
Cold,  28,  40,  246. 
Colophony,  574. 
Coloring  matter,  590. 
Combination,  laws  of,  70,  148,  267. 
Combining  proportionals,  269. 
Combustion,  111,  114. 

complete,  115,435. 

incomplete,  116,  436. 

in  chlorine,  152. 

in  oxygen,  58,  63. 

slow,  140. 

spontaneous,  106,  140 

with  sulphur,  131. 

under  water,  142. 
Conductors  of  heat,  42. 
Conicine,  597. 
Contact,  459. 
Copper,  348. 

"       alloys  of,  364. 
"      and 'sulphur,  131,  362 
"      oxide  of,  349. 
"      salts  of,  173,359. 
Cordials,  501,  562. 
Corrosive  sublimate,  373. 
Cotton,  431. 
Creosote,  438. 
Crystallization,  50,  125,  155. 

•"  interrupted,  51. 

"  water  of,  54. 

Cudbear,  594. 

Curcumine,  592.  • 

Cyanic  acid,  179. 
Cyanide  of  potassium,  291. 
Cyanogen,  157. 


D. 

Daguerreotype,  381. 
Dammara  resin,  570. 
Daturine,  597. 
Davy's  safety-lamp,  114. 
Decay,  443. 


674 


INDEX. 


Decimal  weights  and  measures,  10. 
Deoxidation,  144,  198. 

"  retrospect  of,  418. 

Dephlegmator,  191. 
Detonation,  160. 
Dew,  44. 

"    point,  38. 
Dextrine,  460. 
Diamond,  107. 
Diastase,  461. 
Diffusion  of  gases,  165. 
Digestion,  635. 
Dimorphy,  108,  126,  274. 
Disinfectants,  105,  152. 
Distillation,  41. 

"          dry,  119,  436. 
Dobereiner's  lamp,  85. 
Dragon's-blood,  570. 
Dyeing,  595. 
Dyes,  591. 

E. 

Earths,  252. 

"      alkaline,  237. 

"      metals  of  the,  252. 
Egg-shells,  624. 
Ehvyle,  502. 
Electrophorus,  577. 
Elements,  ancient,  19. 

"        retrospect  of  chemical,  41 8 
Elutriation,  256. 
Emetine,  597. 
Emulsion,  525. 
Epsom  salt,  249. 
Equivalents,  270. 
Ether,  504.  * 

"      sulphuric,  503. 

"     varieties  of,  507. 
Ethyle,  oxide  of,  504. 
Euphorbium,  582. 
Evaporation,  37,  40. 
Excrements,  659. 
Expansion,  22,  27. 
Explosive  gas,  86. 
Extractive  matter,  586,  588. 
Extracts,  585. 


F. 


Faeces,  659. 
Fat  acids,  542. 
Fats,  520. 


Felspar,  265. 
Fermentation,  alcoholic,  482. 

artificial,  519. 

mucilaginous,  515. 

of  bread,  516. 

putrefactive,  445. 

vinegar,  509* 
Ferment  oils,  554. 

"       sediment,  489. 
Fibrine,  636. 
Filtration,  47. 
Fine  mark,  379. 
Finery  process,  281. 
Fire  and  coal,  103. 
Fire,  to  extinguish,  111,  530. 
Fire-damp,  114,  118. 
Fish-oil,  537. 
Flame,  117,  121,  122. 
"      of  a  candle,  122. 
"      shining  of,  117,  529,  560. 
Flax,  429. 
Flesh,  640. 

Floating  of  bodies,  16. 
Fluids,  rising  and  falling  of,  92. 
Fluoric  acid,  190. 
Fluorine,  4. 56. 
Fluor-spar,  247. 
Fly-poison,  411. 
Forces,  6,  20. 
Formic  acid,  602. 
Formula,  chemical,  88. 
Frankincense,  582. 
Frost,  44. 

Fulminic  acid,  179. 
Fumigation,  438,  558,  576. 
Fumigating  spirit,  562. 
Fusel  oil,  554. 
Fusible  metal,  346. 
Fustic,  592. 


G. 

Galena,  341. 
Galipot,  570. 
Gallic  acid,  604. 
Gall,    645. 
Galvano-plastic,  358. 
Gamboge,  582. 
Gases,  99. 

"      collection  of,  56. 
Germination,  426. 
Gilding,  386. 
Glass,  180,  226. 


INDEX. 


575 


Glass,  etching  of,  190 
"      soluble,  204,  226. 
"      to  break,  &c.,  27. 

Glauber  salts,  218. 

Gla/ing,  226,  257,317. 

Glue,  647. 

Gluten,  453,  477. 

Glycerine,  547., 

Glyccryle,  oxide  of,  547. 

Glycocoll,  651. 

Gold,  383. 

"     combinations  of,  386. 
"     mosaic,  325, 
"     parting  of,  384. 

Golden  sulphuret,  407. 

Goulard's  extract,  337. 

Gramme,  10. 

Granulation,  310. 

Grape-juice,  484. 

Graphite,  107. 

Guano,  663. 

Gum  Arabic,  465. 
cherry,  467. 
elastic,  584. 
resins,  582. 
starch,  458. 
teagacanth,  466. 

Gun-cotton,  433. 

Gunpowder,  207. 

Gutta  percha,  584. 

Gypsum,  211. 

"       solution  of,  197. 


Hsematoxyline,  594. 
Hair,  to  remove,  405. 
Haloid  salts,  157,  187,276. 
Halogens,  150,  157. 
Hartshorn,  spirit  of,  228. 
Heat,  22. 

"     conduction  of,  42. 

"    destruction  of  chemical  combi- 
nations by,  57. 
Heat,  expansion  of  air  by,  97. 

solids  by,  27. 

"  "          water  by,  22. 

"    free,  36,  86. 

"     latent,  32,  36. 

"    of  chemical  combination,  86. 

"     radiation  of,  43. 
Hemp,  429. 
Hippuric  acid,  664. 


Hoffmann's  anodyne  liquor,  50* 
Honey,  469. 
Horn-silver,  381. 
Horny  matter,  653. 
Humus,  444. 
Hyalogens,  158. 
Hydrates,  54. 
Hydraulic  cement,  239. 
Hydriodic  acid,  189. 
Hydrobromic  acid,  189. 
Hydrochloric  acid,  184,  185. 
Hydrocyanic  acid,  191. 
Hydrofluoric  acid,  190. 
Hydrogen,  SI,  87. 

"          reduction  by,  357 
Hydrometer,  16. 
Ilydrothionic  acid,  132. 
Hyperoxide,  77,  79. 
Hypocklorous  acid,  178. 


Ice,  formation  of,  29. 
Illuminating  gas,  117. 
Illumination,  115,  529,  560. 
Indigo,  173,  594. 
"      blue,  594. 
Ink,  285,  603. 
Inuline,  457. 
Iodine,  155. 
Iron,  275. 

"    and  chlorine,  289. 

"       "     cyanogen,  290,  293. 

"      "    sulphur,  131,  133,  294. 

"    bar,  280. 

"     cast,  279. 

"     crude,  279. 

"    magnetic  oxide  of,  276. 

"    malleable,  280. 

"    ore,  276. 

"      "    bog,  276. 

"       "    brown,  276. 

"       "     spathic,  276. 

"    oxide  of,  276,  285. 

"        dyeing  with,  197. 

"    rust  of,  276. 

"    scales,  68. 

"    salts  of,  83,  173,  186,  284-  288, 

"    specular,  276. 

"     vitriol,  89,  285. 
Isinglass,  647. 
Isomerism,  1 79,  274,  424. 
Isomorphism,  264,  274. 


676 


INDEX. 


K. 

Kermes,  407. 
Kindling  purposes,  130. 


L. 

Lac-lake  or  Lac-dye,  591. 

Lactic  acid,  457,  515. 

Lactucarium,  582. 

Lac  varnish,  578. 

Lakes,  595. 

Lamp-black,  107,  116,576. 

Lard,  521. 

Laws,  chemical,  70,  148. 

Lead,  329. 

and  sulphur,  341. 
glass,  331. 
.glazing,  257. 
oxide  of,  331. 
plaster,  550. 
salts  of,  160,  198,  334. 
subacetate  of,  337. 
sugar  of,  198,  337. 
tree,  340. 
white,  339. 
Leaf-green,  593. 
Leather,  648. 
Lichenine,  457. 
Lime,  239. 

"    and  chlorine,  244. 
"    as  mortar,  239. 
"    burnt,  238, 
"    carbonate  of,  237,  271. 
"     caustic,  238. 
"    muriate  of,  246. 
"    nitrate  of,  243. 
"    phosphate  of,  242. 
«    slaked,  33. 
"    soap,  240. 
"    sulphate  of,  241,  271. 
"    water,  46,  238. 
Linen,  429. 
Liniment,  541. 
Linseed  oil,  534. 
Liquation  process,  382. 
Liqueurs,  501,  562. 
Litharge,  337. 
Lithographic  stones,  237. 
Litmus,  594. 

"       paper,  48. 
"       solution,  47. 
Loam,  252. 
Logwood,  594. 


Lunar  caustic,  380. 

Lupuline,  598. 

Lye,  caustic,  203,  221. 


M. 

Madder,  591. 
Magnesia,  250. 

"         compounds  of,  .249. 
Magnetic  pyrites,  295. 
Malachite,  349. 
Malic  acid,  601. 
Malt,  426,  460. 
Manganese,  298. 

acids  of,  301. 
black  oxide  of,  297 
oxide  of,  297. 
salts  of,  299. 
Mannite,  474. 

Manuring  by  ammoniacal  salts,  235. 
bones,  658. 
gelatine,  650. 
guano,  663. 
gypsum,  241. 
inorganic  matter,  617. 
lime,  240. 
muriatic  acid,  186. 
organic  matter,  616 
potassa-salts,  214. 
sulphuric  acid,  173. 
Mark,  fine,  379. 
Marsh -gas,  445. 
Marsh's  arsenical  test,  417. 
Mashing  process,  461,  487. 
Mastic,  570. 
Matches,  208. 
Matter,  18. 
Meal,  516. 
Melting,  30. 

point,  31. 
Mercury,  365. 

"         and  sulphur,  376. 
"        oxide  of,  56,  368. 
"        salts  of,  366. 
Metalloids,  56. 

"          and  hydrogen,  192. 

"    oxygen,  192. 
Metallic  alloys.    See  Alloys. 

"        oxides,  retrospect  of,  418, 
Metals,  201. 

"      heavy,  275. 
«      light,  201. 
"      negative,  133. 
"      noble,  379. 


INDEX. 


677 


Metals,  positive,  133. 

"      retrospect  of  the,  41 8. 
Meter,  10. 
Milk,  625. 
Minium,  332. 
Moire  metallique,  326. 
Molvbdcnum,  396. 
Mordant,  197,1595. 
Morine,  592. 
Morphine,  597. 
Mould,  514. 
Mountain  blue,  349. 
Muriatic  acid,  185. 

"        ether,  507. 
Myrrh,  582. 


N. 

Npphtaline,  441. 
Naphtha,  442,  555. 
Nascent  state,  150. 
Neutralization,  71,  160,  186. 

"  capacity  of,  199. 

Nickel,  303. 
Nicotine,  597. 
Nitre,  207. 

"     formation  of,  480, 
Nitric  acid,  159,  161. 

"     oxide,  162. 
Nitrogen,  101. 
Nitro-muriatic  acid,  188. 
Nitrous  acid,  161. 
"      ether,  507. 
"       oxide,  163. 
Non-conductors,  42. 
Non-metallic  elements,  56. 
Nutrition,  plastic  elements  of,  639. 


O. 

Odor,  123. 

CEnanthic  ether,  485. 
Oil,  burning,  to  refine,  535. 
"    gas,  528,  560. 
"    lamp,  529,  560. 
"    soap,  540. 
Oils,  empyreumatic,  555. 
"    ethereal,  551. 
"    fat,  520. 
"    ferment,  554. 
"    volatile,  552. 
Olefiant  gas,  502. 

57* 


Oleic  acid,  546. 
Oleine,  533. 
Oleo-saccharum,  564. 
Olive  oil,  535. 
Opium,  582. 
Orchil,  594. 
Orelline,  592. 
Organic  acids,  193,  598. 
"       bases,  596. 
"       radicals,  508,  513. 
Organogcns,  56,  122. 
Orleana,  592. 
Orpiment,  416. 
Oxalates,  197,  212. 
Oxalic  acid,  196. 
Oxidation,  66. 

«         by  chlorine,  152,  186 
"         by  chlorate  of  potassa,33& 
«         by  nitre,  207. 
"         by  nitric  acid,  1 60. 
"          by  oxygen,  500. 
"         degrees  of,  75,  154,  272. 
Oxides,  69,  77. 

"      retrospect  of,  418. 
Oxidizing  flame,  181. 
Oxygen,  56,  80. 
"       acids,  159. 
"       circulation  of,  167,  614. 
"       salts,  retrospect  of,  183,  41& 


P. 

Palm  oil,  535. 
Papin's  digester,  96. 
Parchment,  648. 
Paste,  457. 
Peas,  starch  of,  452. 
Peat,  446. 
Pectine,  468. 
Perchlorides,  154. 
Permanganic  acid,  301. 
Persio,  594. 

Phosphoric  acid,  65,  176. 
Phosphorous  acid,  177. 
Phosphorus,  138, 

"          oxide  of,  177. 
Phosphuretted  hydrogen,  145. 
Pigments,  590. 
Piperine,  597. 
Pitch,  569,  575. 

"     burnt,  576. 
Plants,  cultivated,  615. 

"      food  of,  614. 


678 


INDEX. 


Plants,  growth  of,  613,  614. 

44      inorganic  constituents  of,  607. 

"      uncultivated,  614. 
Platinum,  390. 


spongy,  392. 
,  107. 


Plumbago, 

Pneumatic  trough,  60. 
Polish,  578. 
Polychroite,  592. 
Porosity,  106. 
Potash,  201. 
"      lye,  203. 
"      soap,  541. 
Potassa,  203. 

acetate  of,  202. 

antimoniate  of,  403. 

carbonate  of,  201. 

caustic,  203. 

chlorate  of,  59,  203. 

chromate  of,  398. 

muriate  of,  209. 

nitrate  of,  207. 

oxalate  of,  197,  212. 

silicate  of,  204,  226. 

sulphate  of,  206. 

tartrate  of,  194,  211. 
Potassium,  205. 

and  chlorine,  209. 
"    iodine,  210. 
"     sulphur,  213. 
ferricyanide  of,  293. 
ferrocyanide  of,  291. 
Potato-starch,  451,  462. 
Precipitation,  129. 

Preservation  of  organic  matter,  449. 
Proportions,  chemical,  272. 
Proteine,  477. 
Protochlorides,  150. 
Prussian  blue,  290. 
Prussiate  of  potassa,  291,  293. 
Prussic  acid,  290. 
Puddling  process,  281. 
Putrefaction,  445. 

"  to  prevent,  105,  449. 

Pyrogens,  123,  149. 
Pyrometer,  26. 
Pyrophorus,  338. 
Pyroxylic  spirit,  439. 


Quartation,  384. 
Quartz,  183. 
Quercitron,  592. 
Quinine,- 5  97. 


Racemic  acid,  599. 
Radicals,  199. 

"        compound,  508,  513. 
Rape-oil,  535. 

Rat  electuary,  139.  ^ 

Reagents,  133. 

"        for  acetic  acid,  198. 
"          "    ammonia,  229. 

antimony,  407. 

arsenic,  413,  416,  417 

bismuth,  347. 

carbonic  acid,  46,  102 

chlorine,  186. 

copper,  152,  192. 

gold,  388. 

hydrosulph.  acid,  479 

iodine,  155. 

iron,  296. 

lead,  335. 

lime,  197,  241,  256. 

magnesia,  251. 

manganese,  300. 

mercury,  375. 

muriatic  acid,  186. 

nitric  acid,  160. 

oxalic  acid,  197. 

phosphoric  acid,  176. 

platinum,  394. 

potassa,  211. 

silver,  381. 

soda,  404. 

starch,  457,  645. 

sugar,  645. 

sulphuric  acid,  171, 240 

tartaric  acid,  194. 

the  rnetals,  133. 

tin,  322,  325. 

zinc,  312. 
retrospect  of  the,  149. 
"        synopsis  of,  page  657. 
Realgar,  416. 
Rectification,  492. 
Reduction  by  hydrogen,  357. 
"          dry,  144,  198,  355. 
"          flame,  181. 
"          galvanic,  358. 
"          humid,  285,  356. 
Refining,  384. 
Rennet,  628. 
Resin,  569,  570. 
Respiration,  167,  639. 

"  elements  of,  639. 

Retrospect  of  alcohol,  £c.,  519. 


INDEX. 


67D 


Retrospect  of  animal  matter,  665. 

"  the    albuminous    sub- 

stances, 481. 
Retrospect  of  the  alkalies,  236. 

"  "      alkaline  earths,  251. 

"      earths,  266. 

„         "  "      extractive  and  col- 

oring substances,  597. 
Retrospect  of  the  halogens,  157. 

"  "      heavy  metals,  328, 

395,418. 

"  *«      hydrogen  acids,  191. 

"      light  metal.s,  266. 
"      metallic  sulphurets, 

418. 

«      metalloids,  158. 
u      metals,  266. 
"      organogens,  122. 
"      oxygen  acids,  183. 
"      pyrogens,  149. 
"      resins  and  oils,  584. 
"      vegetable  acids,  198. 
"      vegetable  bases,  597. 
"          of  vegetable  matter,  618. 
of  vegetable  tissue,  starch, 

sugar,  &c.,  476. 
Rotation  of  crops,  617. 
Rum,  484. 
Rum-ether,  507. 


S. 


Safety-lamp,  114. 
Saf  'ty-tube,  92. 
Safflower,  591. 
Saffron,  592. 
Sago,  446. 
Sal-ammoniac,  229. 
Salt,  common,  215,  216. 

"          "         volatilization  of,  182. 

"    double,  261,  267. 
Salting  of  qjeat,  644. 
Saltpetre,  207. 
Salt  radical,  199. 
"     springs,  216. 
Salts,  71,  160,  267. 

**     acid,  194,  197. 

"     basic,  202,  347. 
Sandal- wood,  591. 
Sandarach,  570. 
Sap-green,  593. 
Scheele's  green,  414. 
Schweinfurth  green,  414. 
Sealing-wax,  575. 


Selenium,  137. 
Sellers  water,  165 
Shellac,  570. 
Shot,  343. 
Silica,  183. 
Silicon,  158. 
Silver,  379. 

"      alloys  of,  379. 
Silvering,  386. 
Silver,  oxide  of,  381. 

"      salts  of,  3SO. 
Simp,  459,  472. 
Smalt,  304. 
Smell,  123. 
Smelting,  278. 
Smoking  of  meat,  438. 
Show,  43. 
Soap,  540. 

"    resinous,  580. 
Soda,  220,  221. 

"    biborate  of,  225. 

"     carbonate  of,  220 

"    caustic,  221. 

"    lye,  221. 

"     muriate  of,  173,  186,  215 

"    nitrate  of,  224. 

"     phosphate  of,  223. 

"     silicate  of,  226. 

"     soap,  540. 

"     sulphate  of,  173,  218. 

"     sulphite  of,  174. 
Sodium,  222. 

"        and  chlorine,  153,  215 
"         "     oxygen,  67,  81. 
"         "     sulphur,  219. 
Solanine,  597. 
Soldering,  225. 
Solution,  45. 
Soot,  107,  116,  576. 
Soup,  643. 
Spar,  heavy,  248. 
Spermaceti,  538. 
Spirit,  498. 
Spritz-bottle,  94. 
Stalactites,  237. 
Starch,  450. 

"      gum,  458. 

"       sirup,  459. 

"      sugar,  459. 
Steam,  35. 
Stcaric  acid,  545. 
Stearine,  533. 
Steel,  282. 
Stick-lac,  570. 
Stochiometry,  70,  267 


680 


INDEX. 


Strontium,  248. 
Strychnine,  594. 
Sublimate,  128,  373. 
Sublimation,  128. 
Suboxide,  77. 
Succinic  acid,  606. 
Sugar,  469. 

"      burnt,  475. 
"      cane,  470. 
"      fermentation  of,  482. 
"      liquid,  472. 
"      of  gelatine,  651. 
"      of  milk,  473,  629. 
"      of  starch,  469. 
«*      sorts  of,  459,  469. 
Sulphur,  123. 

"       amorphous,  127,  129. 
Sulphuret  of  ammonium,  231. 
*'         antimony,  407. 
"         arsenic,  416. 
««         calcium,  220,  405. 
M         copper,  362. 
«         iron,  131,  133,  294. 
«*         lead,  133,  341. 
"         manganese,  300. 
"         mercury,  376. 
"         potassium,  213. 
"         silver,  381. 
"         tin,  325. 
«          zinc?  312. 
Sulphuret:  sulphide,  131,  154. 
Sulphurets,  metallic,  133. 

"  "      retrospect  of  the, 

418. 

Sulphur,  flowers  of,  128. 
"        liver  of,  213. 
"         springs,  137. 
Sulphuric  acid,  anhydrous,  169. 
"  "    common,  168,  172. 

"  "    fuming,  170. 

"  «    hydrated,  172. 

"  "    mixing  of,  with  water, 

84,  173. 
Sulphuric  acid,  Nordhausen,  170. 

"        ether,  506. 
Sulphurous  acid,  64,  174. 
Superficial  fermentation,  488. 
Symbols,  chemical,  88. 
Synthesis,  7. 


T. 

Tallow,  522. 

"      soap,  540 


Tannic  acid,  603. 
Tannin,  603. 
Tanning,  648. 

"        substances,  605. 
Tar,  pit-coal,  441. 
Tartar,  194,  211. 

"       emetic,  406. 
Tartaric  acid,  194. 
Tartarus,  195. 
Taste,  123. 

Temperature,  24,  113. 
Test-paper,  48. 
Test-tubes,  34. 
Theory,  7. 
Thermometer,  24. 

"  spirit,  25. 

Tin,  316. 

"    alloys  of,  318. 

"    and  sulphur,  325. 

"    glaze,  317. 

"    moir6,  326. 

"    oxide  of,  317,  326. 

"    proof,  318. 

"    salts  of,  319. 
Tinning,  229,  327. 
Tombac,  364. 
Tragacanth,  466. 
Train  oil,  537. 
Tufa,  calcareous,  237. 
Turmeric,  592. 
Turpentine,  568. 

"          oil  of,  551. 
Type-metal,  409. 


U. 


Uranium,  328. 
Urea,  661. 
Uric  acid,  662. 
Urine,  660. 


V. 


Value,  379. 
Vapor,  37,  99. 

"      cold,  40. 
Varnish,  534. 

lac,  578. 
Vat,  cold,  594. 
Vegetable  acids,  193,  598. 

"        albumen,  451. 

"        ashes,  607. 

"         caseine,  452. 


INDEX.    * 


Vegetable  fats,  534. 

growth,  614. 
jelly,  468. 
life,  419. 
mucus,  466. 
tissue,  427. 
Veratrine,  597. 
Verdigris,  36 1/ 
Vermilion,  376. 
Vinegar,  198,  509. 

"        aromatic,  198,  563. 

"        mother,  527. 

"       quick  method  of  making, 

511. 
Vital  air,  80. 

"     force,  80. 
Vitriol,  285. 
"      blue,  175. 
"      green,  89,  285. 
"      oil  of,  170. 
"      white,  312. 


W. 

Water,  21. 

"      as  food  for  plants,  614. 
"      bath,  149. 

boiling  of,  34,  95,  96. 

chemically  combined,  54. 

composition  of,  55,  87. 

decomposition  of,  55,  82,  83. 

distilled,  41,  561. 

expansion  of,  by  cold,  28. 
"  by  heat,  22. 

in  the  air,  100,  102. 

mineral,  165,447. 

of  constitution,  159,  196. 


Water  of  crystallization,  54. 
«*     soft  and  hard,  237. 

Wax,  539. 

Weather-prophets,  93. 

Weighing,  81. 

Weight,  absolute,  10. 
"       due,  379. 
"      specific,  11. 

Weights,  9. 

"       apothecaries',  9. 

Weld,  592. 

Wheat-starch,  453. 

Whey,  629. 

White  precipitate,  374. 

Wine,  484. 

Woad,  594. 

Wolfram,  396. 

Wood,  427,  433. 
"      tar,  119,430. 
"     vinegar,  119,  437 
"     white  rotten,  449. 

Woody  fibre,  428. 

Wool,  653. 


Y. 

Yeast,  488. 

"  bottom,  489. 
Yellow  berries.  592. 
Yolk  of  eggs,  623. 


Z. 

Zinc,  309. 

"     oxide  of,  310. 
"     salts  of,  311. 


CORRECTIONS. 


THE  following  corrections  have  been  made  in  the. 
sixth  German  edition  of  the  Chemistry. 

Page  66,  section  75  should  read  as  follows  :  —  "75.  Degrees  of  Oxidation. 
Oxygen  is  a  universal  food  for  all  elements ;  it  is  consumed  by  them,  and, 
as  already  stated,  in  fixed  quantities.  But  the  appetite  of  an  element  for 
oxygen  often  varies,  according  to  the  circumstances  under  which  the  latter 
is  presented  to  it ;  for  example,  it  is  greater  under  the  influence  of  heat 
than  of  cold,  greater  where  there  is  an  excess  than  where  there  is  a  defi- 
ciency of  oxygen  According  to  a  late  discovery,  oxygen,  by  remaining 
for  some  time  in  contact  with  wet  phosphorus,  or  by  being  electrified,  ac- 
quires a  very  great  inclination  to  combine- with  other  bodies.  The  name 
Ozone  has  for  the  present  been  given  to  this  '  chemically  excited '  oxygen, 
the  nature  of  which  has  not  yet  been  fully  investigated.  Many  elements 
consume  a  greater  quantity  of  oxygen  at  a  high  than  at  a  low  temperature, 
and  when  the -sup ply  is  copious  than  when  it  is  deficient ;  and  this  excess 
or  diminution  of  consumption  is  likewise  prescribed  by  fixed  laws.  The 
different  proportions  in  which  substances  unite  with  oxygen  are  called  its 
degrees  of  oxidation" 

Page  130,  insert  immediately  before  section  140:  —  "According  to  a  late 
discovery,  phosphorus  undergoes  a  remarkable  change  by  being  kept  dur- 
ing several  days  at  the  temperature  of  240°  ;  it  then  acquires  a  red  color, 
neither  ignites  nor  dissolves  so  readily,  and  has  lost  its  luminous  power  ; 
but  exposure  to  a  stronger  heat  restores  it  to  its  original  state." 


RECOMMENDATIONS. 


Extract  from  a  Letter  of  S.  L.  DANA,  M.  D.,  LL.  D. 

"The  name  of  the  author  of  the  above  work,  so  well  known  among 
practical  men  as  one  of  the  editors  of  the  Polytcchnisches  Centralblatt, 
would  alone  authorize  the  conclusion,  that  this  book  is  preeminently 
clear,  concise,  practical  in  all  its  allusions  to  art,  simple  in  its  ar- 
rangements, and  illustrated  by  experiments  requiring  no  array  of 
costly  apparatus.  It  is  a  work  worthy  of  its  author.  It  is  a  work 
not  written  for  those  only  who  know  the  position  of  Dr.  Stockhardt, 
and  who  therefore  would  be  prepared  to  welcome  it,  in  its  excellent 
F.nglish  dress,  because  it  approaches  with  the  prestige  of  a  good 
name.  It  is  a  work  which  will  bear  the  character  we  have  given  to 
it,  even  when  subjected  to  the  severest  scrutiny  of  critical  strangers.'* 

From  A.  A.  HAYES,  M.  D.,  Assayer  to  the  State  of  Massachusetts. 

"After  reading  this  work  in  the  translation  by  Dr.  Peirce,  I  have 
formed  the  opinion  that,  as  an  easy  introduction  of  the  student  to  the 
principles  of  chemistry,  it  is  unrivalled  by  any  book  in  our  language. 
The  author  has  adapted  his  illustrations  with  great  sagacity  to  the 
wants  which  students  feel  in  first  entering  upon  the  subject  of  this 
science,  and  there  is  a  directness  and  accuracy  in  his  mode  of  teaching 
which  leads  one  forward  with  great  rapidity.  Rarely  is  it  possible  to 
find  an  elementary  work,  which,  without  being  voluminous,  discusses 
so  many  subjects  clearly.  The  thanks  of  instructors  and  pupils  are 
truly  deserved  by  Dr.  Peirce,  for  placing  this  book  within  their  reach." 

From  JOHN  A.  PORTER,  Professor  of  Chemistry  applied  to  Art,  in 
Brown  University. 

"  Stockhardt's  •'  Principles  of  Chemistry '  occupies  the  first  rank 
among  introductions  to  the  science  of  which  it  treats.  In  Germany, 
where  works  of  the  kind  abound,  it  is  held  in  the  highest  estimation. 


I  hope,  for  the  interest  of  the  science,  that  it  may  he  generally  intro- 
duced in  this  country.  I  concur  entirely  in  the  views  of  the  work 
expressed  by  Professor  Horsford  in  the  Introduction,  and  shall  recom- 
mend it  to  those  pursuing  the  study  of  chemistry  under  my  direction." 

From  ELBRIDGE  SMITH,  Master  of  the  Cambridge  High  School. 

"Cambridge,  Oct.  Uth,  1850.. 
"Ma.  BARTLETT:  — 

*'  Dear  Sir,  —  Of  the  *  Principles  of  Chemistry,'  which  you  sent  me 
some  time  since,  I  can  hardly  speak  too  highly.  It  is  unquestionably 
the  best  book  on  elementary  chemistry  that  has  been  published  in  the 
United  States.  On  first  examining  the  volume,  I  was  inclined  to 
think  that  for  common  schools  it  might  with  advantage  be  abridged. 
A  more  intimate  acquaintance  with  the  work  has  convinced  me  that 
not  a  page  can  be  safely  dispensed  with." 

From  DAVID  A.  WELLS,  Assistant  in  the  Chemical   Department  of 
the  Lawrence  Scientific  School.  ' 

11  Cambridge,  Feb.  1st,  1851. 

"  I  consider  St&'ckhardt's  '  Principles  of  Chemistry,'  as  an  elemen- 
tary book,  superior  to  any  work  of  the  kind  hitherto  published.  I 
have  recommended  its  introduction  in  a  number  of  cases,  and  in  all 
has  it  given  perfect  satisfaction.  It  has, .moreover,  an  advantage  over 
all  other  works,  that  it  is  at  present  as  complete  as  the  rapid  advance 
of  chemical  science  will  admit." 


Extract  from  PROFESSOR  HORSFORD'S  Introduction. 

"  The  qualifications  of  this  work  as  a  text-book  for  schools  are 
Auch  as  to  leave  little,  if  any  thing,  to  be  desired.  The  classification 
is  exceedingly  convenient.  The  elucidation  of  principles,  and  the 
explanation  of  chemical  phenomena,  are  admirably  clear  and  concise. 
The  summary,  or  retrospect,  at  the  close  of  each  chapter,  presenting 
at  a  glance  the  essential  parts  of  what  has  gone  before,  could  scarcely 
have  been  more  happily  conceived  or  expressed  for  the  wants  of  a 
pupil  or  an  instructor.  The  book  is  also  well  adapted  to  the  wan^s 
of  teachers  who  desire  to  give  occasional  experimental  lectures  at  a 
moderate  expense,  and  of  those  who  design  to  commence  the  study  of 
chemistry,  either  with  or  without  the  aid  of  an  instructor." 


. 


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